P O L I S H A C A D E M Y O F S C I E N C E S

GEOGRAPHIA POLONICA

E d i t o r i a l Board S T A N I S Ł A W L E S Z C Z Y C K I ( E D i T B R - I H - C H I E F ) K A Z I M I E R Z D Z I E W O Ń S K I , J E R Z Y K O S T R O W I C K I P I O T R K O R G E Ł L I , J A N U S Z P A S Z Y Ń S K I T E R E S A L I J E W S K A ( S E G R E T A R Y )

Address of E d i t o r i a l Board

K R A K O W S K I E P R Z E D M I E Ś C I E 30 0 0 - 9 2 7 W A R S Z A W A P 0 1 A N D

P r i n t e d in P o l a n d

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P O L I S H A D A D E M Y O F S C I E N C E S I N S T I T U T E O F G E O G R A P H Y

A N D S P A T I A L O R G A N I Z A T I O N

GEOGRAPHIA POLONICA

41 P W H — P o l i s h S c i e n t i f i c P u b i i s f i e r s • W a r s z a w a 1978

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Human I m p a c t on the P h y s i c o - g e o g r a p h i c a l Processes

Proceedings of the Second P o l i s h - H u n g a r i a n S e m i n a r B u d a p e s t , September 1 9 7 5

Edited by

M A R I O N P E C S I and L E S Z E K S T A R X E L w i t h the assistance of

S Y L W I A G I L E W S K A

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CONTENTS

Preface - ( . 5 Marton Pecsi: Landslides at Dunafoldvar in 1970 and 1974 7 Leszek Starkel: The role of extreme meteorological events in the shaping of

mountain relief 13 Adam Kertesz, Jeno Szilard: Some problems of slope development reflected in

slope-profile investigations 21 Wojciech Froehlich: The role of land use in varying the suspended load during

continuous rainfal l (Kamienica Nawojowska catchment, flysch Carpathians) 27 Sandor Somogyi: Regulated rivers in Hungary 39 January Słupik: Potential for change in the water cycle on cultivated slopes 55 Kazimierz Więckowski: The silting processes of the artificial water reservoirs

in the Polish Lowland 63 Sandor Marosi, Sandor Papp: Landscape factors modified by agricultural

activity 73 Leon Kozacki: Changes in the geographical environment as a result of open

mining • 81

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PREFACE

The present volume contains nine reports read at the Second Polish-Hunga-rian Seminar, which was organized by the Geographical Research Institute of the Hungarian Academy of Sciences and held at Budapest on September 11-15, 1975.

Participants were nine Hungarian geographers and seven Polish geogra-phers. The topic discussed was: "The Effect of Man's Activities upon Physi-co-geographical Processes". Altogether fourteen papers were read; they com-mented on the methods applied by the authors, and upon their effect on vari-ous physico-geographical processes resulting from different human activities (agriculture, forestry, hydrography, industry and mining). Much attention was also paid to forecasting what evolution of the geographical environment was to be expected from man's endeavours.

This Seminar reflects the co-operation initiated in 1973 by the Symposium held in September 1973 at Szymbark near Gorlice. The material dealt with at this meeting has been published in Fôldrajzi Értesitô, vol. 23, No. 2, 1974.

Academician Marton Pécsi — Director, Geographical Research Insti tute Hungarian Academy of Sciences, Budapest

Professor Dr. Leszek Starkel Insti tute of Geography and Spatial Ore aization, Polish Academy of Sciences Head of Department of Physical Geography, Cracow

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GEOGRAPHIA POLONICA 41, 1979

L A N D S L I D E S A T D U N A F O L D V A R I N 1970 A N D 1974

MARTON PECSI

Geographical Research Institute, Hungarian Academy of Sciences, Budapest

1. PRECONDITIONS FOR THE LANDSLIDE

(a) The Dunafoldvar landslide belongs to the type of imbricated slice-slides (M. Pecsi, 1972, 1975). It was formed under particular morpholithogenetic con-ditions. The thick loess cover of the Mezofold ends on the right bank of the Dan-ube in steep, high bluffs. The various loess sandy and loamy layers of the some 50 m thick loess sequence are in a nearly horizontal position on the impervious Pannonian clay substratum (Figure 1). The clayey strata are situated at the le-vel of the Danube. The Pannonian clay provides favourable conditions for the formation of a sliding plane: its inclination is only slight or horizontal though its surface is somewhat uneven.

(b) The hydrogeological condition favourable for imbricated slice-slides is provided by the percolation of water at the contact of the permeable clay layers and the loess sequence. Wherever and whenever the waters seeping through these layers are not tapped by springs at the foot of the bluff, the lower layers in the loess sequence are highly saturated. At the site of the Dunafoldvar land-slide this process was supported by a slight trench-like depression, i.e. a buried flat valley coming from NW to the Danube situated on the impermeable clays. In the contact zone, enormous amounts of water seeping through and accumu-lating below the surface are a common phenomenon after wet seasons or wet years.

The summer was very wet in 1970 and the amount of precipitation during the year prior to the date of the landslide was more than 600 mm. The annual average precipitation in Dunafoldvar and its closest environs is about 500 and 550 mm. The Oreg-hegy in Dunafoldvar is a relatively small isolated loess butte where rainwater will run off mostly along the deep loess roads. It was at the site of this butte that the landslide took place for a length of some 700 m south of the 1560 km river post. An above-average precipitation is not enough to saturate the 40-50 m thick loess sequence, let alone to provide enough water for the springs. The springs are fed by groundwater at the foot of the bluff on the shore of the Danube. The water supply of groundwater probably comes from the valley west of the loess butte running along the "background" Mezofold. The bottom of this valley is 100 m a.s.l. at Dunafoldvar and it decreases to 98 m to the south. On the basis of the examination of the cross-section we may pre-sume that this level is between that of the red clay and the dark-grey loamy soil overlying the Pannonian clay. It is very much the same as the vertical po-sition of the slightly pink-coloured sandy, loess-like layers in the lowest 4 to 5 m of the Dunafoldvar bluff. Possibly percolation of water takes place at the

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8 M. Pecsi

Fig. 1. The Dunafoldvar r iver-bank landslide to the South of the Danube's ki lometre mark

1 — loess sequence in primary position (autochthonus); l! — loess recently displaced by sliding; 12 — waste of earlier slides; hi — pale pink sandy loess; o — talus; z — earth mound and Pannonian clay upward f rom the Danube's stream bed; f l — fossil soils; ta — dark-grey clayey

loam soil; pa — Pannonian clay; va — red clay; cs — sliding plane

bottom of the layers along earlier small buried valleys. This means that the sequence of the loess layers will not be soaked from above but water will rise f rom the base upwards, depending on the nature of the rock, the intensity of percolation and the pressure exerted by the overlying layers.

(c) Earlier and recent landslides. Prior to the landslide of 15 Sept. 1970 there were several movements in the same place in the Dunafoldvar bluff (Figure 1). As a result of the earlier landslides the loess bluff 150 m a.s.l. has retreated in a section of some 50 to 70 m in width. The bulk that slid down earlier re-sulted in the formation of a bench 115 to 120 m a.s.l. On the bank of the Dan-ube (92.5 m a.s.l.) this also ends in a bluff. This bench has virtually become sta-bilized; houses have been constructed on it since.

Months prior to the 1970 landslide fissures became visible on the loess pla-teau, parallel to the steep rim. The network of these fissures was reported by local people to have become gradually wider and deeper. These people were conscious of slight movements in the days prior to the landslide. The landslide in question resulted in the movement of a slice of loess with an average width of 30 m and a length of some 700 m removing a semi-circular slice from the bluff. The thickness of this slice may have been some 45 to 50 m. The bulk in question was some one million m3 and it crashed down vertically some 30 m as compared to its original position. At the time of the landslide a great noise was heard and dust-clouds were produced. In the bed of the Danube, near to the shore and in front of the sliding surface two arcs of islands nearly parallel with each other were produced and pushed up 2 to 5 m above the water level (Figure 2). People who were present at the time of the landslide saw waves more than 1 m high being produced and hitting against the opposite bank with great force. The surface of the slice became covered by talus on the side of the bluff, while towards the Danube a trench 3 to 5 m wide was formed and, be-tween these, parallel ridges 2 to 4 m high were formed. The bench to the left of the earlier landslide became dissected by broad fissures, and ridges 2 to 4 m wide either rose up or subsided. On the edge of this bench near to the Danube vertical movement was slightest. The horizontal movement of the sliding bulk

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A n n e x t o t h e ar t ic le by L. Kozacki Geograph ia Polonica 41, 1979

P W N W a r s z a w a 1979

Fig. 3. A map of changed relief of post-mining areas — phase III (on the basis of aerial photographs and field observations) 1 — Slope formed by dissection of surface during removal of overburden: a — up to 2 m high, b — 2-5 m high, c — more than 5 m high, 2 — Slopes of undulating-indented outline, 3 — A former course of the slope poorly visible, 4 — Surface of outer dump, 5 — Surface of inner dump, 6 — Traces of removal of coal or overburden, 7 — Surface of unlevelled dumping of ground masses, 8 — Longitudinal dumping ramparts, 9 — Slopes of outer dump formed by large-scale processes (downfalls, slumpings, creepings, etc.), 10 — Downfalls and slumpings in slope area of unchanged surfaces, 11 — Slope of outer dump slightly changed by wash-downs, 12 — Large slumping tongues in area of outer dumping, 13 — Area of massive movements on inclined surfaces with small discontinuous slopes (large alluvial cones), 14 — Oval downwarping of surface of inner dump — suffus-ional type, 15 — Small dissections of slopes, 16 — Large dissections of slopes having wide cones at the foot, 17 — Natural slopes formed during slumping and down-falls: a — up to 2 m high, b — 2-5 m high, c — more than 5 m high, 18 — Artificial water basins, 19 — Natural water basins, 20 — Con-

tour lines

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Landslides at Dunafoldvar 9

towards the Danube was greater in the northern section of the landslide, while it seemed less important to the south. This is due to the curve of the landslide reaching the present-day bank of the Danube only in the north. At this point, however, in the foreground of the landslide, the bench formed by the former landslide could counter-balance this weight. The waste of earlier slides became remobilized on the side of the new slide, was dissected by fis-sures, and in some places smaller slices subsided or protruded. The position of the fissures and elevated land slices suggest that the slices produced by the new landslide slid under the old mobilized mass.

2. THE PROCESS OF AN IMBRICATED SLICE SLIDE

In the Dunafoldvar bluff the vertical fissures parallel to the bank became visible when the lower layers in the dry loess sequence lying on top of the red clay bed became saturated to such an extent that the cohesion strength of the grains was weakened. At first the collapse was of a small size* but enough to produce deep ruptures along a network of fissures of about 76 to 85 degrees in slices parallel to the bluff. The disjunction of slices, however, were not yet complete at that time because the disrupted slices were still supported by the bluff, and still remained in situ. This state could have persisted several weeks or even months until the lower loess layer became more and more moistened and the stability of cohesion was abruptly upset as a result of pressure effected by the soil slices. This phenomenon took place at a time when there was a crit-ical value balance of moisture and pressure. At the time when sudden over-balance occurred in the basal loess layer the overburden dropped with force into the moistened flexible clayey base underneath. In the case of the imbrica-ted slide at Dunafoldvar the potential sliding-plane was pre-formed in the con-tact zone of the nearly horizontal substratum of Pannonian clay and the loess sequence overlying it. The huge bulk of the loess slices exerted great pressure and slid along the flat depressed curve along the preformed sliding plane. In the foreground of the bulk that slid down, the plastic Pannonian clays protru-ded, exhibiting an upwarped and imbricated structure. The landslide at Duna-foldvar on this occasion resulted in the formation of two island arches that emerged from the river bed.

The low ridges off the headland appear like islands and consist of Panno-nian clay and red clay overlying it; those nearer to the bank emerged from the material of the two lowest layers of the bluff, which slid into the Danube as a result of earlier landslides.

The imbricated slide at Dunafoldvar is a peculiar type of landslide which differs from other slump-slide types (M. Pecsi, 1968, 1971, 1972).

The imbricated slice-slide is characterized by the following: (a) the potential sliding-plane is preformed due to the geomorphological and

geological conditions; (b) the imbricated slide and the sliding-plane will be formed in most cases

at the edge of loess bluffs on impermeable clays lying in a horizontal position at the base level of erosion. The slide slightly undercuts the steep bluff;

* The speed with which a collapse occurs in the loess (Vi) is closely connected with the coefficient of fi l tration (K = cm/s) and with the t ime necessary for saturation (t/s) when the thickness of the loess is H. The saturated layer of loess is affected also by the na ture of the loess sequences, and their weight (p/kg/cm2).

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Photo 1. Inner "island" which was formed as a result of the slide-induced upwarping of Pannonian clays of the stream bed overlain by red clays

13 M. Pecsi

(c) the moistening effect of the pervious layer conducting the filtrating wa-ters percolating above the Pannonian clay; or of the intercalated uppermost Pannonian sandy layers; or in places where the first artesitan watertable was undercut by the river channel and was later buried by slope sediments;

(d) the moistened lower layers of the loess complex will loose their stability of pressure and at a critical state of pressure and moisture shearing will take place;

(e) the thick slices of loess that crashed down will move with a rotating, sli-ding motion on the preformed sliding-plane and the horizontal displacement of the mass is only slight.

On the other hand, in the case of slump-like landslides the sliding plane will be formed within the mass of the clay where shearing would take place and the semi-cylindrical surface of rupture will become the new sliding-plane. This means that the potential sliding-plane is neither technically nor geologically preformed. Moreover, there are important differences between these two types of mass movement (imbricated slide and slump) in their hydrogeological and hydrometeorological preconditions. Surface saturation is an important factor in the case of slumps, while in the case of imbricated slides seismic movements are very important besides various other preconditions.

On the basis of observations those parts of the bluffs along the Danube are prone to landsliding where above the Pannonian clay a heavy filtration of ground water takes place or springs are active. Such sections of the bluff will be found along transverse fractures and also in cross-sections of former valleys buried by loess. Periodical landslides will take place when several favourable

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Landslides at Dunaföldvar 11

factors operate simultaneously, or occur at the same time. These include: years of heavy rainfall, important changes in the Danube water level, light seismic movements and artificial damming up of the water.

Photo 2. The Dunaföldvär r iver-bank landslide and its surroundings

LITERATURE

Adam, L., Marosi, S., Szilard, J., 1959, A Mezofold termeszeti fdldrazja (Physical geo-graphy of the Mezofold region), Budapest, Akademiai. Kwiado.

Adam, L., 1957, Suvadasos formak a Tolnai-dombsag loszos teriiletein (Forms of land-slide in the loess region of Tolna Hill Country), Foldr. Ert., 16, pp. 133-150.

Cholnoky, J., 1926, A foldfelszin formainak ismerete (Morfologia) (The knowledge of the relief forms of the Earth's surface. Morphology), Budapest, Egyetemi Nyomda.

Domjan, J., 1952, A kozep-dunai magas partok csuszasai (Slides in the bluffs of the Midlle-Danube), Hidr. Kdzl., 32, pp. 416-422.

Kezdi, A., 1970, Talapmechanika II (Soil mechanics II), Budapest, Tankonyvkiado Vallalat.

Langne Bucko, E., 1969, A csuszamlasok genetikai tipusai (Genetic types of land-slides), Foldr. Ert., 18, pp. 241-245.

Pecsi, M., 1967, Osszefuggesek a lejtomorfologia es a negyedkori lejtoiiledekek ko-zott (Relationship between slope geomorphology and Quaternary slope sedimen-tation), Acta Geologica Hung., 11, 1-3, pp. 307-321.

Pecsi, M., 1968, A lejtoiiledekek fo tipusai es felhalmozodasuk dinamikaja (The main types of slope sediments and the dynamics of their accumulation), Foldr. Ert., 17, pp. 1-15.

Pecsi, M., 1972, The main types of landslides, International Geographical Union 1972: I, Montreal., Univ. of Toronto Press, pp. 54-55.

Pecsi, M., 1975, Geomorphology (Mass movement on the Earth's surface), Budapest,

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12 M. Pecsi

UNESCO, (International Post-Graduate Course on the Principles and Methods of Engineering Geology).

Popov, I. V., 1959, Inzhenernaya Geologiya (Engineering geology), Izd. M.G.U.r

Moszkva. Strahler, A. N., 1956, Quantitative slope analysis, Bull Geol. Soc. Am., 63, pp. 571-596. Varnes, D. J., 1958, Landslide types and processes, "Landslide and Engineering P r a c -

tice", Highway Research Board, Special Report 29, Washington, D. C. Zaruba, Q., Mencl, V., 1969, Landslides and their control, Prague Elsevier (coedition

with the Publishing House of the Czechoslovak Academy of Sciences).

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GEOGRAPHIA POLONICA 41, 1979

T H E R O L E O F E X T R E M E M E T E O R O L O G I C A L E V E N T S I N T H E S H A P I N G O F M O U N T A I N R E L I E F

LESZEK STARKEL

Institute of Geography and Spatial Organization, Polish Academy of Sciences, Cracow

I N T R O D U C T I O N

The role of extreme meteorological events in the evolution of both slopes and valley floors is widely discussed in geomorphic literature. Whenever the activities of man disturb the dynamic equilibrium climate-soil-vegetation (Tri-cart and Cailleux, 1973) one may talk about catastrophic events. These limit production and they are often a danger to human life. However, the results of extreme events are not always dangerous as they do not hinder human acti-vity. The extreme events I regard as short-term events which occur less than once a year (mostly once every few hundred years or every few tens of years). They disturb the dynamic equilibrium of both slopes and valley floors either created in climax conditions of a given morphoclimatic region or inherited from an earlier period. Those events are most intense and most frequent in en-vironments with a disturbed equilibrium (Starkel, 1976).

In the present paper I concentrate on the extreme meteorological events (excluding the strong winds). These include: (a) rapid downpours of high intensity, mainly local in range and connected

with convection currents of the passage of cyclones; (b) long-lasting continuous rains of lesser intensity and regional extent due

to advection of oceanic air-masses; (c) years and/or seasons with both precipitation amounts exceeding the mean

values and low temperatures permitting the saturation of ground; (d) periods of rapid warming (thaws) causing the quick melting of snow and

ice as well as ground-thaw, often associated with precipitation. The extreme events can be considered either in terms of meteorological cause or from the viewpoint of their geomorphological effects.

Meteorological phenomena may be compared by analysis of their intensity (amount of daily rainfall, mean and maximal intensity expressed in millimetres per hour and per minute) and frequency (not occurring each year, recurring in each century or even during the Holocene).

The morphological results of extreme events can be analysed both quanti-tatively (volume of mass displaced, index of slope lowering) and as relief-for-ming effects, i.e. the creation of new forms.

There is a diversity of viewpoints on the role of extreme events in the shaping of relief. Wolman and Miller (1960) analysing the activity of streams, stress events of medium-intensity rather than those of extreme character both in transportation (with as much as 90% of suspended load carried by rivers

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14 L. Starkel

during floods with recurrence periods of less than 5 years) and in the shaping of landforms (assuming the bankfull stage as critical). Mieshtcheriakov (1970) ascribes only a local role to them. However, Tricart (1963), Mortensen (1963), Rapp (1963, 1974), several Soviet geomorphologists (e.g., Rayonirovaniye SSSR, 1965) and the present author stress their importance in the fashioning of relief, although their effects may vary in particular zones of climate. Unfortunately, it is difficult to evaluate exactly the extreme events because of a lack of a dense network of research stations. Different phenomena are misinterpreted: The in-dices of slope denudation (often being much higher) are mainly based on meas-urements of suspended load in large rivers. The magnitude of relief change (creation of new forms) is deduced from multiyear measurements of slope wash and creep only. .

THE MECHANISM OF CHANGES DURING THE EXTREME EVENTS

The occurrence of extreme geomorphological phenomena is controlled by the critical, limiting values of water circulation which depends on the volume, du-ration and intensity of precipitation, and on the ground features (Fig. 1). In analysing the slope water circulation model, it is possible to distinguish a few boundary surfaces at which changes in infiltration may allow new or extremely intense processes to occur. The first boundary surface is that of the topsoiL When the infiltration capacity of this soil is surpassed during intense rains, surface runoff begins and slope-wash and linear erosion result. The second boundary surface is the base of the A horizon (or of the arable layer), a surface separating two layers of different water holding capacity. Rapid flows of topsoil may then result. The third boundary surface is that between the regolith (waste mantle) and the bedrock. Water fails to soak into the bedrock and piping channels, mudflows, debris-flows, landslides and slumps result. The fourth boundary surface is formed by the irregular base of jointed rock. The presence of an overburden may lead to landslides and rock-falls.

The fashioning of both stream channels and flood-plains during the ex-treme events is controlled chiefly by the magnitude and violence of increase in discharges, by the load of sediment carried by the rivers and by the kind of

Fig. 1. The effect of varying permeabilities in different near-surface layers and of infil tration depth in the formation of surface and sub-surface run-off .

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Extreme meteorological events 15

river-transported material as well. For this reason, extreme events may cause (i) channel deepening by the unloaded rivers (in resistant bedrock), (ii) the fil-ling in of the stream channels and the building up of the flood-plains by slope material (braided rivers), (iii) increased erosion and deposition associated with the widening and lateral shifting of channels. The channel form becomes then adjusted to the magnitude of both discharge and transportation rate. After-wards the river channel tends to restore a state of balance (Schumm, 1968).

There is a close relationship between the type of rainfall and the occurrence of extreme events. The higher the intensity of rains and the shorter their dura-tion the smaller is the infiltration (Fig. 2). Thus, heavy downpours give rise to slope-wash and debris flows. In wet years with long-lasting rainfalls deep Landslides occur. In the valley floors downpours of local range lead to local changes (except the sjele). Essential changes are the result of continuous rains during which stream levels rise in all drainage basins. On the other hand, chan-nel forms are not altered in wet years with higher water levels, although t he total amounts of river-transported material may be great.

Fig. 2. Model of relationships between rainfall parameters, permeability of wea th -ered rock horizons, depth of infiltration and type of slope and fluvial processes.

during extreme events.

THE INDIVIDUALITY OF MOUNTAIN AREAS

The highest extreme values of precipitation and the greatest morphological changes are observed in mountain areas. Mountains are typified by steep slopes and irregular river-beds of high inclination (Krivolutskiy, 1971; Hewitt, 1972). The vertical zonation of climatic belts each characterized by its distinctive suite of physical-geographic processes is responsible for the differences in both water circulation and importance of the particular extreme events in the ver-tical mountain profile (as altitude increases rapid thaws become more impor-tant). Mountains often show a temperature- and humidity asymmetry (exposure to rain-bearing winds). It is the marginal zone in a compact mountain massif that receives the heaviest precipitation rather than areas situated in the in -

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16 L. Starkel

terior of mountains (Weischet, 1969). At the same time, marginal zones are the most active technically and so most rapidly uplifted and dissected (Starkel, 1972a).

The precipitation inversion, together with the extent of cultivated areas defi-nes the range of the occurrence of both extreme meteorological events and "catastrophic" geomorphological changes that are most frequently recorded in such areas. However, the extreme meteorological phenomena in a given moun-tain group preserve certain zonal features which are determined by the type of air circulation as welle as sets of climate-soil-vegetation systems developed in vertical form.

THE ROLE OF EXTREME PHENOMENA, BEFORE AND AFTER DEFORESTA-TION IN VARIOUS CLIMATIC ZONES

Extreme events may act in a different fashion in the various climatic zones. This problem will be considered by taking as example the humid tropical, arid (steppe and desert) and temperate zones. These are characterized by the diffe-rent shares of continuous rains, downpours and rapid snowmelts.

<a) THE HUMID TROPICAL CLIMATE

In mountain areas of the equatorial zone and in areas with a monsoonal cir-culation the highest precipitation has been recorded. These may be downpours with a considerable intensity (50-300 mm per hour); more often they consist of continuous rains of 500-2000 mm lasting 2-3 days and with intensities of up to 50 mm per hour. While such rainfalls occur only every few ten years, annual daily maxima are 100 mm and the number of days with a precipitation above 50 mm ranges from 1-5 to 20 or more (de Ploy, 1972; Temple, Rapp, 1972; Star-kel, 1972 a,b; Lundgren, Rapp, 1974). The effect of such rainfalls are, for instan-ce, in Tanzania slope changes equivalent to a mean denudation rate of 14 mm. These were due to a rainfall lasting 3 hours which brought about debris flows and mud flows (Temple, Rapp, 1972). In the Darjeeling Hills, the effect of con-tinuous falls of 700-1000 mm causing debris flows is equivalent to a mean denu-dation rate of 200 mm (Starkel, 1972a). The above data refer to deforested areas with steep slopes and they exceed by more than 50-100-fold the observed magni-tude of changes in woodland with a very intense subsurface runoff. At one bankfull stage on the mountain streams, the 5-fold lateral enlargement of the channels (by undercutting of slopes and removal of terrace deposits) or con-siderable channel deepening can take place. Stream beds can also be raised by as much as 10 m in some stretches (local obstacles).

In the humid tropics, extreme phenomena occurring 5-10 times every cen-tury markedly surpass the mean 100-year denudation rate and control the crea-tion of new forms. They also accelerate relief rejuvenation in the uplifted areas.

(b) THE ARID CLIMATE (DESERT AND STEPPE ZONE)

Mountains of the arid zone are intensely fashioned during the heavy down-pours and rapid melting of snow and ice. The latter event is common in the high mountains of Central Asia where it produces sjels. A single sjel can derive as much as 180,000 m3 of material from 1 km2 (Dumitrashko and o-workers, 1970). On the less inclined surfaces, slope-wash and piping play an essential role. They are most effective in areas where the poor vegetation has been destroyed by overgrazing. Such processes are best illustrated by the formation of ravines up to 15 m deep during a 488 mm rainfall lasting less than 12 hours which has been

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Extreme meteorological events 17

observed by the present author in the Rajasthan (Starkel, 1972b). Extreme events are usually so rare that ravines are buried by moving sands. In the White Mountains, California, both erosional form and debris accumulations on the valley floors are clearly discernible after a few hundred years (la Marche, 1968).

In the arid regions extreme events are usually rare but they control the mor-phological evolution. In this zone, the "normal" processes include the effects of rapid downpours. v

(C) THE TEMPERATE CLIMATE

In mountains, such as the Alps, the Carpathians and the Caucasus with 50-2000 mm annual precipitation, there occur both frontal and convectional downpours and continuous rainfalls due to the passage of cyclones, as well as rapid thaws. Continuous falls of 200-500 mm with an intensity usually below 10 mm per hour occur every few years. Downpours exceeding 100 mm (with maximal intensities 3-10 mm per minute) have been recorded locally.

Under natural conditions the equilibrium may be disturbed by exceptional meteorological events such as the downpour of 762 mm in 270 minutes in the Pennsylvanian Appalachians (Hack, Goodlett, 1960).

Detailed continuous measurements (e.g., at Szymbark in the Polish flysch Carpathians) and assessment of the effects of downpours revealed that slope changes caused by slope-wash (denudation rates of a few millimetres, Maru-szczak, Trembaczowski 1959; Slupik, Gil 1972) were greatest' on the beet- and , potato fields. Materials derived from the slopes of less than 20° are laid down on the broad valley floors. During the continuous rainfalls subsurface runoff is predominant and mud flows and debris flows arise then (Starkel, 1960). How-ever, in wet years with periodic continuous rainfalls and low évapotranspi-ration rates deep landslides occur, for instance, in 1913 (Sawicki, 1917) and in 1974 in the flysch Carpathians.

High stream discharges and channel widening due to both continuous rain-falls and rapid snowmelts have been reported from the Roumanian Car-pathians (in 19 70) and from the French Alps (Tricart, 1962). Deforestation of the mountain areas increases discharges and transportation rates. As a result, brai-ded channels are developing in the valleys. However, in the present century gravel extraction, dam construction and channel corrections are the cause of stream channel deepening, even in the accumulational stretches extending along the margin of mountains (Klimek, Starkel, 1974).

THE ROLE OF EXTREME EVENTS IN THE EVOLUTION OF RELIEF

In mountain areas, extreme events lead to modification of the relief which becomes adjusted to the changing climatic and tectonic conditions. Under natu-ral conditions in the belts of mountain forests and meadows, changes in the initial slope form (inherited from the Pleistocene and bearing debris, solifluc-tional and deluvial deposits) are due to tha simultaneity of waste-mantle pro-duction, of a negative denudation balance and of slope dissection by gullies anc chutes. The reduced supply of slope material into the rivers is favourable foi the deepening of channels (Fig. 3).

Deforestation, farming and overgrazing caused changes of process type. The intensity of processes has increased 100-1000 times. New processes - unre-corded before — did appear (topsoil flows, deflation etc.). Both annual and ext reme downpours of local range tend to be more important than the conti-nuous rainfalls. As a consequence, some areas increase in valley density, and

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18 L. Starkel

the deluvial valley fills vary in thickness there. The role of continuous rain-falls is rather that of changing the channel forms, although falls are more dan-gerous on the steep slopes (debris flows).

The extreme processes either accelerate or retard the natural trend of relief evolution. The undermining of slopes during the floods brings about the rejuvenation of uplifted areas. This is the positive feedback effect (Fig. 3). The same phenomenon retards the maturation of slopes in the old mountains and uplands. Because of subsurface runoff in the Holocene, the dissection of slopes inherited from the periglacial morphogenesis is also a new, positive element. The deforestation of such slopes can increase either dissection (accelerated re-juvenation) or slope-wash. This leads to fur ther maturation of the inherited, concave-convex slope forms. The development of the newly-created forms (pro-duced by strong impulses) can be continued during extremely intense pheno-

Fig. 3. Developmental trends in mountain slopes and valley floors during extremely heavy rain

A. Upper portions of the Carpathian valleys: At — deepening of valley floors and slope rejuvenation proceeding upslope (under natural

conditions); A2 — lateral erosion and aggradation of valley floors, slope dissection and building up by

deluvia (after deforestation); B — the Carpathian Foothills (after deforestation) — aggradation of valley floors and at slope

foot due to deposition of deluvia; C — the Darjeeling Hills (in the Himalayas) — zone of uplif t

Ct — stream channel deepening (in forest) C2 — stream channel deepening, lateral erosion and sedimentation, slope degradation (in

deforested areas)

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Extreme meteorological events 19

mena of greater frequency. It is only when the "normal" processes are also intense that such forms can be degraded and slowly fossilized (trough-like val-leys in some cultivated areas).

In the vegetation-free areas with high frequency downpours, rock surfaces are swept bare and the dynamic equilibrium ceases to exist. Rocky deserts are formed as in the Upland of Assam (Starkel, 1972b) and in the mountains of the mediterranean zone. A new equilibrium quite different from the "normal" one is created.

On the contrary, slopes mantled with permeable debris are stable under cli-matic conditions of the Holocene. No essential slope changes take place now. Such slopes have been described by Rapp (1963). On this basis he concludes that the efficiency of the Holocene morphogenesis is rather low. This refers, however, to small areas which cannot be used for different purposes because of skeletal soils and steep gradients. When rainfall of a magnitude unrecorded during the prevailing environmental "equilibrium" does occur in such an area, chute and gully scars persist in the landscape inherited from an earlier mor-phogenesis (flows at Ulvadal).

The trend of mountain-valley evolution also depends on the fact whether or not the modification of both slopes and stream channels takes place at the same time, i.e. during the same meteorological events. According to Tricart (1962), in the Alps the fashioning of slopes and of valley floors is independent. However, data collected by the present author in India and by Rapp in Tanza-nia show that these are simultaneous processes. Variety is due to differences in the amount of precipitation in a given zone and in the maturity of mountain« relief. In the Himalayas typified by steep slopes continuous rainfalls lead to both disturbance of slope equilibrium and river floods which can be increased by the local ponding of streams by landslides. In the broad Alpine valleys the slope material does not always reach the stream channels. In the Carpathians of low-mountain relief slope-wash is most intense during the downpours; deep landslides occur in the wet years, whereas floods on the larger rivers are the result of continuous rainfalls lasting a few days during which surface runoff is accompanied by the increased subsurface runoff.

REFERENCES

Dumitrashko, N. V., et al., 1970, The problem of sjels and their investigation (in Rus-sian), in: Present exogenic geomorphic processes, Moskva, pp. 131-137.

Gil, E., Slupik, J., 1972, The influence of the plant cover and land use on the surface run-off and washdown during heavy rain, Studia Geomorph. Carpatho-Balcanica, 6, pp. 181-190.

Hack, J. T., Goodlett, J. C., 1960, Geomorphology and forest ecology of a mountain region in the central Appalachians, U.S., Geol. Surv. Prof. Pap., 347.

Hewitt , K., 1972, Mountain environment and geomorphic processes, Mount. Geomorph. B.C., Geogr. Ser., 14, pp. 17-34.

Klimek, K., Starkel, L., 1974, History and actual tendency of floodplain development at the border of the Polish Carpathians, in: Report of the Commission on Pre-sent-day Geomorphological Processes (IGU), Gottingen, pp. 185-196.

Krivolucky ' A., E., 1971, Life of the earth's surface — geomorphological problems (in Russian), Moskva.

Lundgren, L., Rapp, A., 1974, A complex landslide with destructive effects on the water supply of Morogoro Town, Tanzania, Geogr. Annaler, 56, A, 3-4, pp. 251-260.

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20 L. Starkel

La Marche, V. C., 1968, Rates of slope degradation as determined f rom botanical evi-dence, White Mountains, California, Geol. Survey Prof. Pap., 352-1, pp. 341-377.

Maruszczak, H., Trembaczowski, J., 1959, Geomorfologiczne skutki gwał townej ulewy w Piaskach Szlacheckich koło Krasnegostawu (Sum.: Geomorphological effects of a cloudburst at Piaski Szlacheckie near Krasnystaw), Ann. UMCS,B, 11, 4, pp. 129-160.

Mescheriakov, Yu. A., 1970, On the theory of exogenic processes (in Russian), in: Present exogenic geomorphic processes, Moskva, pp. 15-22.

Mortensen, H., 1963, Abtragung und Formung, Nachr. Ak. Wiss. Gôttingen, II kl. 13, pp. 17-27.

de Ploy, J., 1972, A quanti tat ive comparison between rainfall erosion capacity in a tropical and a middle-lati tude region, Geogr. Polonica, 23, pp. 141-150.

Rapp, A., 1963, The debris slides at Ulvadal, Western Norway, Nachr. Ak. Wiss. Gôttingen, II kl. 13, pp. 197-210.

Rapp, A., 1974, Slope erosion due to extreme rainfall , with examples f rom tropical and arctic mountains, in: Report of the Commission on Present-day Geomor-phological Processes (IGU), Gôttingen, pp. 118-136.

Rayonirovaniye .... (coll. work), Regionalization of USSR terri tory af ter main 'erosio-nal factors (in Russian), Inst. Geogr., Moskva, 1965.

Sawicki, L., 1917, Die Szymbarker Erdrutschung und andere westgalizische Rutschun-gen des Jahres 1913, Rozpr. Wydz. Mat.-Przyr. PAU, Ser. A, 56, Kraków.

Schumm, S. A., 1968, River adjus tment to altered hydrologie regime — Murrumbidgee River and palaeochannels, Australia, Geol. Surv. Prof. Paper, 598.

Starkel, L., 1960, Rozwój rzeźby Karpat fliszowych w holocenie (Sum.: The develop-ment of the Flysch Carpathian relief during the Holocene), Prace Geogr. IG PAN, 22.

Starkel, L., 1972a, The role of catastrophic rainfall in the shaping of the relief of the Lower Himalaya (Darjeeling Hills), Geogr. Polonica, 21, pp. 103-147.

Starkel, L., 1972b, The modelling of monsoon areas of India as related to catastrophic rainfall, Geogr. Polonica, 23, pp. 151-173.

Starkel, L., 1976, The role of extreme catastrophic meteorological events in the contemporaneous evolution of slopes, in: Geomorphology and Climate, Wiley and Sons, London, pp. 203-246.

Temple, P. H., Rapp, A., 1972, Landslides in the Mgeta area, Western Uluguru Mts., Tanzania, Geogr. Annaler, 54, A, 3-4, pp. 157-193.

Tricart, J. et coll., 1962, Mécanismes normaux et phenomenes catastrophiques dans l'évolution des versants du bassin du Guil (Htes Alpes, France), Zeitschr. f . Geo-morph., 5, 2, pp. 277-301.

Tricart, J., Cailleux, A., 1972, Introduction to climatic geomorphology, Longman. Weischet, W., 1969, Klimatologische Regeln zur Vertikalverteilung der Niederschlàge

in Tropengebirgen, Die Erde, 100, 2, pp. 287-306. Wolman, M. C., Miller, J. P., 1950, Magnitude and frequency of forces in geomorphic

processes, J. Geol., 68, 1, pp. 54-74.

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GEOGRAPHIA POLON1CA 41, 1979

S O M E P R O B L E M S O F S L O P E D E V E L O P M E N T R E F L E C T E D I N S L O P E - P R O F I L E I N V E S T I G A T I O N S

A D A M KERTESZ, JENO SZILARD

Geographical Research Institute, Hungarian Academy of Sciences, Budapest

The basic problem of slope development concerning morphology and mor-phography is the following: what kind of forms develop on the slopes under cer-tain conditions and as a result of a given dominant force, or forces, fur ther-more what the course is, and a prognosis of slope development? Yet slopes are not only the subject of geomorphological research, but also included in the study of soil erosion, water movement, etc. Part of the varied form? of human activity also takes place on slopes. In a broader sense, the greater part of areas classified as plains may be regarded as aggregates of slopes. Thus the investigation of the problems of slope development is important not only from the theoretical point of view, but its practical importance is likewise enormous.

It follows from the foregoing that experts in technical and agricultural sciences also deal with the problems of slope formation. These branches of science are not interested primarily in the form that comes into existence as a result of processes. Engineers and agricultural experts investigate, e.g., the effect of a specific technical or agricultural intervention.

Geography and more specifically geomorphology has investigated several aspects of slope formation by applying widely differing methods. It is also right to expect a great variety of methods, since the exploration of the laws of slope development is a hard and complicated task. The combined effect of a great number of factors must be analysed and evaluated in a complex way. Here we do not wish to enumerate the methods applied in the course of diffe-rent investigations: we only want to draw attention to a solution — intended to be an experiment — that could contribute to the solution of the above men-tioned problem. This method is the investigation of soil profiles.

The problem of the investigation of slope profiles may be discussed in both an inductive and a deductive way. This latter approach is concerned with the general theory of the formation of slope profiles, while the inductive method draws its conclusions from an analysis of a great number of slope profiles examined in the field. We have adopted the inductive approach in our investi-gations.

A B R I E F D E S C R I P T I O N O F T H E M E T H O D O F S L O P E P R O F I L E A N A L Y S I S

A detailed morphometric field survey of slopes (by means of theodolites) on rationally selected different slope segments is completed. The next step is a comparison of the profiles plotted from detailed topographic maps, and also

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22 A. Kertesz, J. Szilard

with the information available from local profiles and exposures in the field. The final aim of the investigations is to establish — on the basis of morpho-m e t r y analysis of numerous slope profiles and the investigation or the evalua-tion of several borehole data of field surveys — the processes that are respon-sible for the formation of individual slope profiles.

Several authors have dealt with the problem of slope profile analysis. We mention, in particular, the relevant works of A. N. Strahler, R. A. G. Savigear and A. Young. A common feature of the works of these authors is that they discuss the morphometric and mathematical aspects of the problem and pay less attention to the relationship between form and process.

The following problems arise in connection with the survey of slope profiles: 1. field of investigation, 2. selection of the site of profiles, 3. selection of length of slope profile.

1. FIELD OF INVESTIGATION

Before marking the site of profiles in the field, we must, first of all, decide what kind of slopes may come into consideration. Our attention is centered on the slopes of plains, hills, or submountainous areas built of loose (mainly loessy-sandy) sediments, formed chiefly by derasional activity and presently under cultivation. This delimination implies that in the course of the present investigation of our area generally we have concentrated on the analysis of slopes with a relatively small inclination and a longer profile. We did not deal, however, with short and steep slopes mostly formed by slope-mass movement. These latter form the subject of our current special investigations and the re-levant results will be published in separate studies.

2. SELECTION OF THE SITE OF PROFILES

This is an important question because slopes are surfaces, thus their study as a plane section perpendicular to sea level is a simplification that depends greatly on the selection of the site of a given slope profile. A fur ther require-ment is that profiles should follow the direction and trend of the greatest incli-nation of slopes. The surface is often so uneven that in the course of field measurement as well as while plotting from a map it is nearly impossible to mark accurately the direction of the greatest inclination. Thus it seems most effective to mark slope profiles in those places where contour lines run roughly parallel to each other (Strahler, 1956). An additional problem arises if the greatest inclination suddenly changes direction (A. F. Pitty, 1966). It may lead to fur ther inaccuracy if the dense vegetation or tall buildings found along the profile force us to make a detour while surveying.

Two solutions are possible when profile sites are selected: either we choose the profile that appears to be the best and most suitable, or we select it accor-ding to some statistical principle, at random. This latter solution seems to be more reliable and more exact, though we have to reckon with the fact that in this way unwanted profiles become part of our series, besides the above mentioned difficulties (vegetation, buildings) that may disturb the survey. Thus it is more convenient to mark the profile sites on the basis of field prospecting. In the course of our survey of about 60 profiles, we have adhered to this prin-ciple. 3. DETERMINATION OF THE LENGTH OF PROFILES

Slope profiles may traverse several valleys and ridges, and may run as far as the boundary of the area studied. In practice it is usually the profiles of a given valley-side which are selected: thus we measure from the valley bottom

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Slope-profile investigations 23

to the watershed. The profiles of a valley or ridge can be studied f rom time to time. It is doubtful, however, if the boundary of a form-group with similar genesis may be drawn at the watershed, which we have selected as an arbitrary boundary for our profile. Furthermore it is difficult to mark the watershed accurately.

There are various propositions on how to determine the length of slope profiles. The upper boundary of the profile should be drawn in every case in the field, according to its exact orographic position.

After these preliminary remarks, we would discuss the conclusion that can be drawn from the examination of these surveyed slope profiles.

The necessity of the use of theodolites in field surveys is well justified by the difference that exists between field surveys and profiles plotted from to-pographic maps. The differences revealed by the comparison of field surveys and profiles plotted on the basis of detailed topographic maps show the micro-forms of slopes (Figure 1). Thus the morphometric field surveys show the slight unevenness, steps, steep sections within short distances, crevices, small concave and convex sections of slopes, while these are not recognizable on mapped profiles. The occurrence and frequency of micro-forms affect the nature of physical processes acting on slopes, they alter the general process of develop-ment, and influence slope formation as a whole.

Fig. 1. Slope profile on the Majdan-plateau in a WSW-ENE direction Shaded sections indicate the differences between the data obtained f rom maps and the data

obtained from measurements in the field. Vertical exaggeration is 2X.

The above mentioned micro-forms can be — depending on ecological con-ditions — eliminated as a result of anthropogenic activity, but at the same time they may develop fur ther and become indicators of renewed diversified slope development. In spite of the limited extent of their influence at present, their inclusion is well justified.

On the basis of the evaluation of morphometric profiles it is possible to separate the individual types of slopes presently infuenced by anthropogenic activity. This is pi special importance, because up to now slopes have been classified merely into a few basic forms, and even detailed analyses do not show to what extent these basic forms are combined, in what order and ratio etc. do the convex, concave, and straight slope sections alternate. The knowl-edge of the above is very essential concerning fu ture slope development and in assessing the favourable and unfavourable endowments of slopes, so that they are used optimally.

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24 A. Kertesz, J. Szilard

On the basis of our slope-profile investigations, still in the initial stage, we have observed the following:

1. The slope sections of several slope profiles plotted from detailed maps can be characterized by concave curves, while they appear in the field sur-veys as various combinations of convex, concave and straight parts (Figure 2). The ratio of convex and straight sections within the profile recorded as gene-rally convex was 55-60 per cent. In these cases no depositional tendency asserts itself and degrading neutral and accumulating sections alternate along the profile. Looking for the cause, we find that in these profiles there occur frequent but mostly secondary dissections of relief. Apart from this, the above mentio-ned profiles serve as an example of how far field investigations modify former more general conclusions.

Fig. 2. Slope profile on the Farkas-mountain on a SW-NE slope d — convex slope segment h — concave slope segment

Besides this, detailed profile investigations brought to light that on the concave, lower parts of slope sections the rate of accumulation is not always proportional to the size and degree of degradation of the slopes. In several profiles there was scarcely any accumulated soil material on these concave strips. This may be due to several causes; in most cases it simply means that the zone of accumulation is a narrow strip and the bulk of the fine-grained sediment — degraded from the upper segments of the slopes — is washed di-rectly into local channels and is thus transported fur ther downslope. In some cases — mostly in wind grooves — deflation also plays a role in the transloca-tion of material.

2. The straight and steeper slope segments or the gradually sloping seg-ments plotted from maps were primarily gently convex slope sections on the basis of field investigations, and intermediate small depressions with gently

Fig. 3. Slope profile on the Negyokros hegy on a NNW-SSE slope 1 — well marked steps 2 — hardly noticeable steps

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Slope-profile investigations 25

convex sections occurred only secondarily (Figure 3). Where these latter were frequent, degradation was greatly restricted and even on the intermediate con-vex sections was confined to narrow strips.

3. Slightly convex or straight slope segments are dominant in about 70-80 per cent of cases characteristic of these steps. Concave profiles occur very rare-ly, they are generally confined to the narrow upper strips of these "landings", where they are connected to the steeper profiles or may be limited to small depressions. Some of the material degraded from the upper levels accumulates on these steps. This typical feature of these steps may be due to the fact that these forms are mostly stable surfaces though slightly eroded. The almost intact soil profiles indicate a state of equilibrium in degradation and accumu-lation. The slightly convex curve of the profiles seems to indicate that the percentage value of the eroded material transported to the landings from the upper slope sections is roughly identical with the amount eroded f rom there.

4. The steepest strips of the slopes that are either straight, or slightly convex or concave curves, represent those sections that are the most intensively degraded and are presently developing. The soil-forming rocks are found most-ly near to the surface or else thin cultivated soils are typical.

Connected with the intensive degradation of these slope segments is their high mobility and the fact that they change their site, depending on local factors, quite frequently towards shifting the top levels. On the basis of de-tailed profile investigations and mapping (S. Marosi, J. Szilard, 1969), the man-ner in which these steep slope segments move on the slopes, can be described. On the slope segments that were formally eroded down to the parent mate-rial and later abandoned by the steep retreating slope sections, recently form-ed culture soils are found. These culture soils of differing character and thickness lying on the lower parts of the now moderate slopes indicate the direction of movement along the slopes. At the same time, towards the top levels the gradually thickening soil profile testifies to a reduced degradation in the direction of movement as the slopes become less steep. This phenomenon may recur — depending on the nature of the slope — at several sites. It occurs not only along the longitudinal slope profile, but also spreading sideways at several sites, depending on the dissection of the slope.

5. On the basis of 36 representative soil-profile analyses taken in the foregrounds of the .Buda Mts. and the Velence Mts., and in the hilly region of Somogy we were able to conclude that the longest slopes were measured on pe-diment surfaces, and the relatively shorter ones on the uplifted marginal areas. The length of slope ranged between 94 and 570 m. On the basis of present data concernig the relationship between the length of soil profiles and the height of slopes, we may establish that the average inclination of long-slopes is smal-

Fig. 4. Slope profile on the Farkas-mountain on a NNW-SSE slope e — straight slope segment

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2 6 A. Kertesz, J. Szilard

le r . In t h e case of s lopes sho r t e r t h a n 200 m, w h e r e t he t r i a n g l e is cons t ruc t ed f r o m t h e base of t h e s lope and t he he igh t of t h e slope, t h e a v e r a g e va lue of t h e c o t a n g e n t of t he ang l e w i t h the base of t h e s lope w a s 6.89, w h i l e th is v a l u e c h a n g e d in t he case of slopes longer t h a n 200 m to 9.57.

W e sha l l c a r r y on w i t h these inves t iga t ions in t he f u t u r e . A m u c h l a r g e r n u m b e r of p ro f i l e s h a v e to be s u r v e y e d in d i f f e r e n t a r e a s f o r t h e s ta t i s t ica l a n a l y s i s of m o r p h o m e t r i c da ta . T h u s the v a l u e of t he gene ra l i za t ions wi l l be g r e a t e r a n d t he f o r m a t i o n of t y p e s wi l l be possible . T h e recogn i t ion and a n a -lysis of these types can se rve as t he basis f o r an op t ima l economic use of slopes.

REFERENCES

Marosi, S., Szilard, J., 1969, A lejtofejlodes nehany kerdese a talajkepzodes es a ta -lajpusztulas tiikreben. (Some questions of slope development, with regard to soil formation and soil deterioration), FdldrH Ert., 18, pp. 53-67.

Pit ty, A. F., 1966, Some problems in the location and delimitation of slope profiles, Zeitschrift fur Geomorphologie, 14, pp. 383-391.

Savigear, R. A. G., 1956, Technique and terminology in the investigation of slope forms, Slopes Comm. Rep., 1, pp. 66-75.

Savigear, R. A. G., 1965, A technique of morphological mapping, Ann. Ass. Am. Geogr., 55, pp. 514-538.

Savigear, R. A. G., 1967, The analysis and classification of slope profile forms, Slopes Comm. Rep., 5, pp. 271-290.

Strahler , A. N., 1956, Quantitative slope analysis, Bull. Geol. Soc. Am., 67, pp. 571-596. Young, A., 1961, Characteristics and limiting slope angles, Zeitschrift fur Geo-

morphologie, 5, pp. 126-131. Young, A., 1964a, Slope profile analysis, Slopes Comm. Rep., 3, pp. 45-66. Young, A., 1964b, In discussion on slope profiles: a symposium, Geogr. J., 130, pp.

80-82. /

' Young, A., 1971. Slope profile analysis: the system of best units, Inst. Br. Geogr. Spec. Publ., 3, pp. 1-13.

Young, A., 1972, Slopes, London. Longman.

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GEOGRAPHIA POLONICA 41, 1979

T H E R O L E O F L A N D U S E I N V A R Y I N G T H E S U S P E N D E D L O A D D U R I N G C O N T I N U O U S R A I N F A L L ( K A M I E N I C A N A W O J O W S K A

C A T C H M E N T , F L Y S C H C A R P A T H I A N S )

WOJCIECH FROEHLICH

Institute of Geography and Spatial Organization, Polish Academy of Sciences, Cracow

The Carpathian river valleys experience catastrophic floods every few years. Floods are the result of continuous rainfall with daily amounts exceed-ing 100 mm (T. Niedźwiedź, 1972). Floods play the major role in channel transformation and they are moving waste materials accumulated in the val-ley-floors at flood-free intervals (K. Brykowicz et al., 1972; W. Froehlich, 1972; M. Gałka, 1973; M. Klimaszewski, 1935; M. Niemirowski, 1972; L. Starkel, 1972; M. Woźnowski, 1935; A. Zierhoffer, 1935; T. Ziętara, 1968, 1974). Both intensity and magnitude of the waste removal process is reflected in the sus-pended sediment transport. During floods the Carpathian rivers can carry more than half of the material transported per year (J. Brański, 1968; J . Cyberski, 1969; W. Froehlich, 1972; Z. Kajetanowicz, 1938; A. Welc, 1972; H. Ziemska, 1928). For this reason, detailed studies of the then removed material are neces-sary to know the extreme intensities of the present-day waste removal from the Carpathian flysch catchments.

Both the activities of man and land use affect the transport of materials by rivers (J. Douglas, 1967). Researches into the mechanism of sediment transport-ation during floods and of waste supply from the small catchments with various land use have as yet been lacking.

P U R P O S E A N D M E T H O D S O F S T U D Y

The paper includes the author's preliminary results of continuous measure-ment of sediment carried by the river Kamienica Nawojowska and its tr ibu-taries: the Krysciow and the Homerka (Fig. 1). The purpose of study is to explain the influence of land use on the variation in both waste supply and waste removal from the Krysciow and the Homerka drainage basins (compared to the Kamienica Nawojowska catchment) during the 1972 flood.

Measurements were made of the water turbidity in the hydrometric sec-tions at the stream mouths. During the flood, 1 litre water samples were collect-ed from the current by dip-bottles at intervals of 1-2 hours. The suspended sediment concentration was determined by filtration and weighing.

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28 W. Froehlich

Fig. 1. Map of the study area 1 — river system, 2 — watersheds, 3 — forest, 4 — height spots, 5 — meteorological stations,

6 — rain gauges, 7 — limnigraphs, 8 — water gauges

THE STUDY AREA

The Kamienica Nawojowska catchment of 239 km2 is situated in the eastern part of the Sącz Beskid Mts. and it rises to between 280 and 1084 m a.s.l. The drainage basin as a whole consists chiefly of the flysch (sandstone-shale-marl) Magura series. Only in the north-western part of the area, i.e. in the Sącz Ba-sin is a complex of Miocene clay and sand overlain by Quaternary alluvia. The Kamienica Nawojowska valley comprises both gaps cut in solid rock and ba-sin-like widenings filled with fluvial gravel and boulders. Those conditions, together with the irregular valley gradients tend to favour sediment supply and removal.

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The role of land use 29

The land use pattern in the Kamienica Nawojowska catchment is related to both altitudinal zonation and relief types. In the Beskidian high-mountain zone of steep slopes and skeletal mountain-soils woodland is predominant. For-esj occupies some 35.6% of the catchment area. In this zone the narrow and fo-rested (in 82%) Kryściów drainage basin of 7.03 km2 is situated (Table 1). The narrow valley floor and the steeply inclined valley- and hill-sides are unfavour-able for settlement and farming. In the low-mountain and high-foothill zone arable grounds occupy 35.6% of the Kamienica Nawojowska catchment. Slopes contain deep loamy-silty waste mantles with a small admixture of sharp-edged debris. Their liability to washing shows seasonal variations. It depends on the compactness of the soil aggregates and on the moisture content.

TABLE 1. Characteristics of the geographical environment of the catchment basins

Catchment basin

Kamienica Na-wojowska River 239 1082-280 32.2 18.1 — — 42.7 8.7 35.6 Homerka Stream 19.55 1060-370 10.7 57.0 2.60 4.6 51.8 7.0 38.2 Kryściów Stream 7.03 1082-520 7.1 53.3 2.41 2.2 82.0 — —

In the wide Homerka drainage basin (19.55 km2) intermediate and high foothills are common. Arable grounds (38.2% of the area) extend far into the Homerka valley. Forest covers 51.8% of the area and is mainly concentrated in the headwaters. In the Homerka basin, the land use pattern and the pro-portions between cultivated area and woodland are similar to those in the Kamienica Nawojowska catchment.

In the latter one woods are intensively exploited now and show a dense network of roads and timber tracks. These are responsible for a diminution of flood control by forest. Furthermore, they are the source areas of great amounts of fine waste transported in suspension. In areas under cultivation the patchwork of fields is associated with a grid of roads. Apart from the field furrows, roads increase the natural drainage density. They also accelerate the water cycle in the catchment and provide abundant waste (K. Figuła, 1960, 1966; P. Prochal, 1958; J. Słupik, 1973; W. Froehlich, 1975).

Shape and size are essential parameters by which both drainage basins differ. These parameters determine both lag time and flood wave concentra-tion. Although attempts have been made to explain the influence of basin shape in a theoretical way (A. N. Strahler, 1964) this problem has as yet not been studied in the Carpathian catchments.

THE HYDROLOGICAL REGIME OF THE KAMIENICA NAWOJOWSKA

The Kamienica Nawojowska drainage basin receives on an average 872 mm of precipitation per year. Rains are most intense during the summer. Single downpours which occur every few years may exceed 100 mm per 24 hours and produce catastrophic floods. In the winter snowfall occurs.

Drain- L a n d use (%) Height Length Gra- a g e Road

Area above of dient d e n s i t y density meadow ^ ]

(km2) sea-level river of river (km/ f o r e s t and (m) (km) (%o) /km2) / k m 2 ) Pasture ^

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30 W. Froehlich

The Kamienica Nawojowska is a typical Beskidian river with a rain — snow — ground regime of supply. Its annual mean discharge at Nowy Sącz was 3.4 m8/s in 1961-1970, and it oscillated from 1.9 m3/s in 1961 to 5.5 m3/s in 1970. In the autumn and winter, during very low water discharge falls below 0.5 m8/s. Spring peak discharges caused by snow melt reach as much as 70 m8/s. Maximum discharges recorded during catastrophic floods which occur every several years may exceed 300 m8/s (W. Froehlich, 1975).

At low stage the Kamienica Nawojowska carries 2-8 g/m8 of fine waste. The suspended sediment concentration increases many times during violent river floods caused by excessive rainfall and it may exceed 13 kg/m8 (on 19 July, 1970). With similar flood discharges, the r iver can carry varying suspended loads (W. Froehlich, 1975).

THE HYDROLOGICAL CHARACTERISTICS OF FLOODS

The flood of August 1972 was the result of continuous rainfall lasting f rom 19 to 23 August. Rain gauges installed at the outlet of the Krysciów and Ho-merka catchments recorded a total precipitation of 115 mm then (Table 2). The daily precipitation total at the Krysciów mouth was 70 mm on 20 August. This equals to some 12°/o of the annual precipitation total. The magnitude of the flood described was much lower than that of the catastrophic flood which occurred in the Carpathians in July 1970. The parameters of both floods are contained in Table 3.

During the flood described streamflow began to rise on 20 August. A di-rect run-off response to the rainfall was produced in the catchments of the

TABLE 2. Hydrologie parameters of the rainfall floods of July 1970 and August 1972

Catchment basin

Maximum discharge (m3/s)

1970 1972

Specific run-off (m3/s)

1970 1972

Run-off from basin (m3)

1970 1972

Kamienica Na-wojowska River Homerka Stream Kryściów Stream

314 187 — 15.12 — 5.60

1,314 782 — 773 — 797

38,183,000 23,960,448 — 1,445,126 — 513,646

TABLE 3. Parameters of the suspended sediment transport during the rainfall floods of July 1970 and August 1972

Catchment basin

Maximal turbidity

(g/m3) 1970 1972

Total amount of suspended load

(t) 1970 1972

Mass of suspended sediment (amount

per 1 sq. km) 1970 1972

Kamienica Na-wojowska River 13,498 9,188 285,769 — 1,196 t 195 t Homerka Stream — 9,630 — 2,154 — 110 t Kryściów Stream — 4,292 — 366 — 52 t

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The role of land use 31

A U G U S T 1972

Fig. 2. Diagram of changes in s t ream discharge (Q) and suspended sediment concen-tration (Cs) during the flood of August 1972 in the Kamienica Nawojowska River*

Kryściów and the Homerka. A few hours later discharge increased at Nowy Sącz on the Kamienica Nawojowska (Figs 2, 3 and 4). Changes in water level recorded by limnigraphs coincide with those of rainfall intensities. The flood wave consisted of several peaks. Discharges reached their maximum in the morning of 21st August: 187 m3/s (782 1/s/km2) on the Kamienica Nawojowska; 15.12 m3/s (773 1/s/km2) on the Homerka; 5.60 m8/s (797 1/s/km2) on the Kryś-ciów. Although 82% of the area is forested the specific run-off in the Kryściów catchment was much higher at peak flow than that in the drainage basin as a whole. This suggests that the small basin width and the very dense network of both natural and artificial incisions brought about the shortening of lag time and flood wave concentration. Compared with the Homerka drainage basin, the rapid run-off was not reduced in woodland. The only effect was that the streamflow was falling more slowly in the final phase of the flood there (Fig. 4).

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32 W. Froehlich

A U G U S T 197?

Fig. 3. Diagram of changes in stream discharge (Q) and the suspended sediment concentration (Cs) during the flood of August 1972 in the Homerka Stream

THE REMOVAL OF FINE WASTE IN SUSPENSION

During the flood, the course of changes in suspended sediment concentra-tion reflected the flood wave shape. On the streams Kryściów and Homerka the peak suspended sediment concentration (turbidity) occurred before the corresponding streamflow peaks. This situation is related to the increased slope wash and rapid material supply by the network of artificial incisions adjacent to the stream channels.

n the Kamienica Nawojowska the maximum turbidity of 9188 g/m3 and the maximum discharge of 187 m3/s coincided. This can be explained by the combined effect of the first flood waves that were contributed by the small catchments, and by the increased sediments production in the stream channel which became adjusted to the hydrodynamic conditions of the bankfull stage.

The peak suspended sediment concentration observed on the Homerka was 9630 g/m3. This value approximates to that for the Kamienica Nawojowska

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The role of land use 33

Fig. 4. Diagram of changes in stream discharge (Q) and suspended sediment concen-tration (Cs) during the flood of August 1972 in the KrySciow Stream

(9188 g/m3), whereas on the Krysciow the peak suspended sediment concentra-tion was only 4292 g/m3.

It appears that with similar discharge, the rivers examined carry different suspended loads. The shape of the turbidity loop reflects the conditions under which the fine waste is provided for transport in suspension (Fig. 5). These loops include a distinct rising limb (rising flow) and a falling limb (recession flow). The different width of the loop can be explained in terms of the varying supply of fine sediment in the various phases of the flood.

Narrow turbidity loops for the Kamienica Nawojowska and the Homerka indicate that conditions were favourable for the increased supply of waste in the various phases of the flood. Such conditions prevail in the lower lying cul-tivated areas. The greatest amounts of sediment are provided by the dense network of roads reflecting the pattern of land ownership. This is responsible for the high values of suspended sediment concentration in the rivers Kamie-nica Nawojowska and Homerka.

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34 W. Froehlich

The broad turbidity loop for the Kryściów can be explained in terms of the retarded sediment supply, especially at falling stage. This may be due to the protective role of forest which reduces both surface run-off and slope wash. In the rock-cut Kryściów stream channel the production of fine material is confined to the short phase of bed load transportation, whereas the wide accu-mulational channel reaches of the Kamienica Nawojowska and the Homerka provide great amounts of fine waste.

THE TRANSPORT BALANCE

/ (

The volume of sediment removed in suspension represents the sum of trans-ported materials that were recorded in the various phases of the flood. The amount of suspended load removed from the Kamienica Nawojowska catch-

Fig. 5. Diagram of changes in the concentration of suspended material (Cs) in relation to the discharge (Q) during the flood of August 1972 in the:

A — Kamienica Nawojowska River, B — Homerka Stream, C — Kryściów Stream

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The role of land use 35

ment was 41,533 tons (174 t/km2). 2,154 tons (112 t/km2) were removed along the Homerka stream channel, and 366 tons (52 t/km2) of fine material were taken away from the Kryściów catchment.

More than 95% of the suspended sediment removed by the flood were trans-ported in its early phase which comprises 40% of duration. It appears that waste removal f rom the drainage basins of mountain rivers is most intense at rising stage. In plans for reservoir constructions and hydrotechnical develop-ments on the streams considerations should, therefore, be taken of the extreme values of sediment transported in the early phase of the flood. The frequently cited annual mean values can be exceeded many times during a single flood.

Results show that in the Kamienica Nawojowska catchment the removal of waste takes place with varying intensities. Differences are clearly important when the amounts of material removed per unit area are being considered in the different drainage basins. The small amounts of material taken away from the Kryściów basin show that the waste removal process is retarded in wood-land. Its protective role is both diminished and masked by the dense network of artificial incisions.

At present, the activities of man and land util ization clearly influence the course and intensity of waste removal from the Carpathian flysch catchments.

According to- K. Klimek et al. (1972), high discharges leading to violent flooding may have been influenced by deforestation of the Carpathian drainage basins. This is indicated by the high frequency of coarse fractions of sediment forming the river mud in the Wisłoka valley. Studies by M. Niemirowski (1972) also revealed that the intensity of the present-day processes of erosion is lower in well forested catchments compared with those where cultivated areas are predominant.

CONCLUSIONS

In the Kamienica Nawojowska catchment floods can remove more than 70%> of the waste transported in suspension per year. In the early phase of the flood which comprises some 40% of duration more than 95% of the suspended sediment is being removed. During the flood described the Kamienica Nawo-jowska carried away 46,537 tons of fine waste which equals to 195 t/km2. On the contrary, in the forested (in 82%) Kryściów catchment and in the cultivated (in 38%) Homerka catchment the corresponding values are 48 and 51 t/km2. The high values of waste removed from the entire Kamienica Nawojowska catch-ment is due to many features. These include the high production of fine ma-terial immediately in the accumulational channel reaches, abrasion of trans-ported material and processes of erosion. For this reason the effects of present-day waste removal during floods supported by measurement on the large rivers should not be extrapolated to the small drainage basins.

Both the course of hydrological phenomena and the rates of waste removal f rom the Kryściów and Homerka catchments suggest that at present it is the various density of artificial incisions (resulting from intense cutting of woods and farming) which essentially influence the above process. Crowded together artificial incisions are typical of the flysch Carpathians (J. Słupik, 1976). Man influences the intensity of waste removal during floods through a dense network of artificial incisions rather than removal of forest. As a consequence, the nat-u ra l stream densities are increased and the water cycle in the catchments accelerated. F u r t h e r m o r e great amounts of material are supplied to the rivers. Thus, the protective role of forest is being reduced. In the Kryściów catchment

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36 W. Froehlich

t h e low va lues of m a x i m u m s u s p e n d e d s e d i m e n t concen t r a t i on and t h e l i m i t e d w a s t e suppl ies in to t he s t r e a m c h a n n e l a re ind ica to rs of t h e d is t inc t i n f l u e n c e of fo res t .

Because of t he d i f f e r e n t bas in shapes a f i r m e s t ima te of bo th i n f l u e n c e of l a n d u t i l iza t ion a n d m a g n i t u d e of w a s t e r e m o v a l d u r i n g f lood is no t poss ib le . T h e basin g e o m e t r y d e t e r m i n e s lag t i m e and f lood w a v e concen t ra t ion . I t a l so m a y d imin i sh t he p ro tec t ive ro le of fo res t . F o r th is reason, f u t u r e h y d r o t e c h -n ica l u n d e r t a k i n g s shou ld p a y m o r e respec t to bas in shapes and land u t i l i z a -t ion, a n d to the e x t r e m e va lues of w a s f e r e m o v a l as well .

REFERENCES

Brański, J., 1968, Zmącenie wody i t ransport rumowiska unoszonego w rzekach pol-skich (Sum.: Water silt charge and transport of suspended load in Polish rivers), Prace PIHM, 95, pp. 49-67.

Brykowicz, K., Rotter, A., Waksmundzki, K., 1972, Hydrographical and morpholo-gical effects of the catastrophic rainfall of July 1970 in the source area of the Vistula, Studia Geomorph. Carpatho-Balcanica, 6, pp. 199-201.

Cyberski, J., 1969, Sedymentacja rumowiska w zbiorniku rożnowskim (Sum.: Sedi-mentation of bed load in the Rożnów basin), Prace PIHM, 96, pp. 21-42.

Douglas, I., 1967, Man, vegetation and the sediment yield of rivers, Nature, 215, pp. 925-928.

Figuła, K., 1960, Erozja w terenach górskich (Sum.: Erosion in highland regions), Wiadomości IMUZ, 4, pp. 109-147.

Figuła, K., 1966, Badania transportu rumowiska w ciekach górskich i podgórskich o różnej budowie geologicznej i użytkowaniu (Sum.: Investigations into t rans-portation of solids in mountain and submountainous watercourses with different structures and util ization), Wiadomości IMUZ, 3, pp. 131-145.

Froehlich, W., 1972, The carrying off of suspended and dissolved load in the Kamie-nica Nawojowska and Łubinka catchment basins during the flood of 1970, * Studia Geomorph. Carpatho-Balcanica, 6, pp. 105-119.

Froehlich, W., 1975, Dynamika transportu jluwialnego Kamienicy Nawo-jowskiej (Sum.: The dynamics of fluvial transport in the Kamienica Nawojowska), Prace Geogr. IG PAN, 114.

Froehlich, W., Klimek, K., Starkel, L., 1972, The Holocene formation of the Dunajec valley floor within the Beskid Sądecki in the light of flood transport and sedi-mentation, Studia Geomorph. Carpatho-Balcanica, 6, pp. 63-83.

Gałka, M., 1973, The course and size of fluvial processes in the Stryszawka channel during the catastrophic flood of July 1970, Studia Geomorph. Carpatho-Balcanica, 7, pp. 143-152.

Kajetanowicz, Z., 1938, Untersuchungsmethoden der Sinkstoffbewegung in den Fliiss-en Siidpolens, VI Baltische Hydrologische Konferenz, Deutschland, August 1938, Bericht 19 D.

Klimaszewski, M., 1935, Morfologiczne skutki powodzi w Małopolsce Zachodniej w lipcu 1934 r. (Rés.: Les consequences morphologiques de la crue d'été dans le Sudouest de la Pologne, Juillet 1934), Czas. Geogr., 13, pp. 283-291.

Koperowa, W., Starkel, L., 1972, Changes in the paleogeography of valley floors dur -ing the Holocene, in: Excursion quide book. Symposium of the INQUA Commis-sion on studies of the Holocene. First part, Poland, September 12-20, 1972, pp. 34-38.

Niedźwiedź, T., 1972, Heavy rainfall in the Polish Carpathians during the flood of July 1970, Studia Geomorph. Carpatho-Balcanica, 6, pp. 194-198.

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The role of land use 37

Niemirowski, M., 1972, Comparison of the effects of floods in two catchment basins of the Gorce Mts. (Beskid Sądecki), Studia Geomorph. Carpatho-Balcanica, 6, pp. 201-203.

Niemirowski, M., 1974, Dynamika współczesnych koryt potoków górskich (na przy-kładzie potoków Jaszcze i Jamne w Gorcach) (Sum.: The dynamics of contempo-rary river-beds in the mountain streams as exemplified by the Jaszcze and J a m -ne in the Gorce Mts), Zeszyty Nauk. UJ, Prace Geogr., 34.

Prochal, P., 1958, Badania sieci hydrograficznej oraz stanu zlewni potoku Biała Wo-da w Jaworkach. (Studies of both hydrographic network and state of the Biała Woda catchment at Jaworki), Rocz. Nauk Rolniczych, 72-F-3, pp. 1273-1279.

Słupik, J., 1973, Zróżnicowanie spływu powierzchniowego na fliszowych stokach gór-skich (Sum.: Differentiation of the surface run-off on the flysch mountain slopes), Dokum. Geogr., 2.

Słupik, J., 1976, Zastosowanie zdjęć lotniczych w określaniu wpływu bruzd i dróg polnych na s t rukturę bilansu wodnego stoków górskich (Sum.: Aerial photo-graphy used to assess the influence of ditches and field paths on the s t ructure of the water balance of mountain slopes), Prace Nauk. Uniw. Śląskiego, 126, Fotointerpretacja w Geografii, 11, pp. 31-38.

Starkel, L., 1972, Observations on the morphological role of heavy rainfall in the Flysch Carpathians in July 1970, Studia Geomorph. Carpatho-Balcanica, 6, pp. 191-194.

Welc, A., 1972, Transportation of suspended matter in the rivers Ropa and Bystrzan-ka and magnitude of wash down during the flood in July 1970, Studia Geomorph. Carpatho-Balcanica, 6, pp. 206-209.

Woźnowski, M., 1935, Skutki powodzi w dolinie Czarnego Czeremosza. Obserwacje z roku 1927 (Effects of a flood in the Czarny Czeremosz valley — observations f rom 1927), Czas. Geogr., 13, pp. 297-299.

Ziemska, H., 1928, Próba spostrzeżeń i badań nad erozją wód Wisłoka (Sum.: An at tempt at some observations and research on the water erosion of the river Wisłok), Czas Geogr., 6, pp. 102-106.

Zierhoffer, A. 1935, Kilka przykładów działania wód powodziowych w dorzeczu Stryja i Oporu (Obserwacje z 1927 r.) (Res.: Quelques effects morphologiques de la crue dans le bassin de Opór — Stryj , aout 1927), Czas. Geogr., 13, pp. 292-297.

Ziętara, T., 1968, Rola gwałtownych ulew i powodzi w modelowaniu rzeźby Beskidów (Sum.: Par t played by torrential rains and floods on the relief of the Beskid Mts.), Prace Geogr. IG PAN, 60.

Ziętara, T., 1974, Uwagi o roli murów w modelowaniu rzeźby Karpat (Sum.: Remarks on mura effect on the modelling of the Carpathian relief), Rocz. Nauk. Dydakt. WSP, Prace Geogr., 6, Kraków, pp. 5-41.

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GEOGRAPHIA POLONICA 41, 1979

R E G U L A T E D R I V E R S I N H U N G A R Y

SANDOR SOMOGYI

Geographical Research Institute, Hungarian Academy of Sciences, Budapest

I

The Hungarian river-system, developed within the Pannonian or Carpathian Basin, one of the geosynclinal areas of the Earth, is undergoing a very inten-sive transformation today. Besides the larger rivers shown in Table 1, there are about 2500 water courses including the smaller ones in Hungary. Their total length amounts to 26,400 km, with a stream-density of exactly 0.27 km/sq. km. Areal distribution is uneven, depending on the amount of precipita-tion, the permeability of the surface and on the inclination.

A high proportion (about a quarter) of the area of Hungary (shown in Fi-gures 1-3) would under natural conditions be constantly or at least periodically inundated. This can be explained by the history of the surface processes. The prevailing hydrographic conditions are due to the subsidence of the Great and Little Plains and of some areas in Transdanubia, from the Late Tertiary and continuing into the Holocene. The marginal depressions were responsible for the rapid transition of the rivers from their mountainous reaches to the plains. Their gradient decreasing, they were forced to deposit their alluvium, forming a series of alluvial cones and meandering around these, without any fixed di-rection. The zones of marginal depressions and alluvial fans were full of poorly drained, slowly infilling closed sub-basins. Owing to the great number of mean-ders, the actual length of the rivers is many times greater than their length measured from the air.

Due to these circumstances the flood waves that occurred in the mountainous catchment areas due to heavy precipitation piled up in the foreland of the mountains on the Great Plain.

The climate of the Carpathian Basin is such that two floods occur on the rivers — the early spring flood results from the snow-melts, and the early summer flood drains the waters of the annual precipitation maxima — the pe-riodically inundated parts of the flood-plains dry out only in the second half of the year and then they are used for stock-breeding. Social and economic activity was limited from the earliest times to the flood-free surface as proved by archeological data. Increasing social demand at the beginning of the 19th century pressed for flood control and the regulation of the rivers became a na-tional task.

Though there existed similar initiatives for other purposes in earlier centu-ries only limited and local results were achieved and it was under the leader-ship of Istvan Szechenyi, President of the National Transport Committee, that

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Fig. 1. Map of the drainage system of the Danube and the Tisza river

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Fig. 2. Hungarian canal system in the area east of the Tisza-river

river control was started with the help of national solidarity and organization' and it was only then that the damage done by rivers could successfully be pre-vented. Under the leadership of outstanding engineers the works were under-taken in the first decades of the last century and continued until the first World War with impressive results.

The most important data about specific rivers are shown in Table 3, while Table 4 contains data on the Tisza, the river that was altered the most. A more than 600 km long new bed was created, many hundred meanders were cut off and the length of the Hungarian rivers was shortened by several thousand ki-lometres.

Beside the new river-beds a 3000 km long embankment was constructed for the protection of the reclaimed flood-plains, the total area of which was 23,600 sq. km (nearly a quarter of the total area of the country). In the humid

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Fig. 3. Areas f requent ly flooded in Hungary before the regulation of the rivers 1 — permanently inundated areas; 2 — periodically inundated areas

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Regulated rivers 43

TABLE 1. The largest rivers in Hungary

Total Catchment On Hungarian territory River length area length catchment

in km in sq. km in km area in sq. km

Düna 2,860 817,000 417 93,000 Mosoni-Duna 120 18,061 113 8,723 Räba 283 10,113 191 4,550 Ipoly 257 5,108 164 1,518 Sio 334 14,728 334 14,726 Dräva 720 40,490 160 6,378 Mura 454 14,138 48 1,987 Tisza 962 157,000 598 47,000 Szamos 415 15,881 50 306 Bodrog 267 13,579 50 972 Sajo 229 12,708 130 4,203 Hernäd 282 4,556 110 1,011 Zagyva 179 5,677 178 5,672 Härmas-Körös 363 27,537 91 12,931 Kettös-Körös 37 10,386 37 1,744 Feher-Körös 236 4,275 8 298 Fekete-Körös 168 4,645 14 151 Sebes-Körös 209 9,119 59 3,155 Berettyo 204 6,095 78 2,649 Hortobägy 163 5,776 163 5,776 Maros 754 30,330 48 357

years the inland waters are pumped from the canals with 265 pumps, the total output amounts to 467 m3/s (as much as the average discharge of the Tisza near Tokaj). The volume of water thus removed exceeds the output of the world-famous embankments in the Netherlands. Their effect can be traced for a long way off in the water-courses, in the changes of the natural conditions of the former flood-plains and also in the economic and social life of the population affected.

From among these varied effects, we are in a position to discuss only those that have taken place with regard to rivers. The main aim to be achieved by the building of embankments was to accelerate the run-off, especially at the times of floods by making cut-offs, and the protection both of the former flood-plains that would be used for agriculture and of the nearby settlements. The shorten-ing of the channels resulted in a steeper gradient and in an increase of the velocity of flow. Since run-off became rapid, flood periods were shortened and the duration of low waters were now longer. The narrow flood-plains were restricted in between the embankments so flood levels rose considerably. As a result, the embankment must be raised even today. The steeper gradient resulted in an increase of energy and this led to the incision of the channel-bed and its deepening. The higher flood level resulted in a smaller volume at low water and the embedding of the river channel and in a more extreme water re-gime. The best example is the change in the water levels of the Tisza river (Table 3, Figure 4).

The reduction of the level of low waters is a consequence of embedding and of. the steeper gradient of the shorter channel, with the resultant faster flow

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44 S. Somogyi

TABLE 2. Data on accomplished river-control works (after S. Somogyi)

River

Length of river before and after

regulation in km

Length of cut-offs in km

Number of cut-offs

Length of meanders

in km

Average fall before and after

regulation in cm/km

Düna" 494 417 — 23" — 5.0" 8' Tiszac 1419 966 — 114 589 — —

Tiszad 1211 758 136 114 589 3.7 6 Drâva 400d 232d 75 68° 243 7.5° 12' Marosd 86 50 — 13 — . 14 24 Harmas-Körösc 234 >.91 34 39 177 2 5 Kettös-Körösc 84 37 23 15 70 4 8 Feher-Körösd 126 67 25 81 84 — —

Feketr-Körösd 166 90 26 61 102 — —

Sebes-Körösd 162 86 53 24 129 — —

Berettyód 269 91 51 46 229 — —

Körösök eqylittd 1041 462 212 266 791 — —

Szamosd 187 108 — 22 26 — —

Bodrog" 76 50 8 8 34 3.5 6 Râba® 132 84 — 80 51 32 47 Temesc 336 194 — 92 —

a Hungarian section; b section south of Dunafftldvdr; c the whole length; d regulated section; e below Sdrvdr

TABLE 3. Data on the regulation of the Tisza river

Abandon- Length Fall Former Present ^ j. anort-

Tisza * length length ^ ening before after regula- regula-

km ^ tion tion

Forras—Tiszabecs 208 208 — — — — —

Tiszabecs—Tokaj 334 208 169 43 38 7.5 12.2 Tokaj—Tiszafured 205 117 113 25 43 3 5.2 Tiszafiired—Csongr&d 326 191 160 25 41.5 2.1 3.7 Csongrdd—Maros- '

torok 99 57 46 14 33 2.5 3.8 Maros-torok—Hatar 31 17 19 5 45 1.9 2.7 Hatar—Torkolat 216 158 82 24 27

1419 966 589 136 32 3.7 6.0

of w a t e r . This has a d i rec t b e a r i n g on sh ipp ing on these r ivers . On the Tisza, f o r example , b e f o r e its r egu la t ion , ships could sail d o w n to V a s a r o s n a m e n y w i t h -out d i f f i cu l ty ; a f t e r the r egu la t ion of t h e r ive r , howeve r , it could be only p e -r iod ica l ly n a v i g a t e d even a r o u n d Szolnok. T h e nav igab i l i t y of t h e Maros a n d t he D r a v a became impossible . T h e D a n u b e — w i t h a m u c h m o r e vo luminous d i scharge — w a s no t i n f l uenced u n f a v o u r a b l y by t he m o d e r a t e sho r t en ing of its bed as a consequence of r i ve r r egu l a t i on . The r e g u l a t e d sect ions r e t a i n

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Regulated rivers 45

TABLE 4. Changes in the water level of the Tisza river

Water gauge Changes of

low-water level Culmination of high waters

to 1890 to 1957 1830-1855 to 1932 to 1970

Vásárosnamény Tokaj Szolnok Csongrád Szeged

ł - 1 4 0 - 1 1 0 - 1 4 0 - 1 5 0 - 1 3 0

- 2 0 5 - 1 7 2 - 2 2 7 - 3 3 5 -235

770 715 683 610 613

832 799 894 929 923

912 872 909 935 960

their dynamic equilibrium and after a certain time try to lengthen their course by developing meanders. The regulated length of the Tisza river has increased from 1890 to 1932 by 5 km. The consequence of the channel deepening and the formation of local meanders was the accumulation of a considerable amount of alluvium. According to estimations, the amount of alluvium deposited by the Tisza, eroding its banks and bed, varied between 60 and 65,000 m3/km2/y, de-pending on the intensity of erosion and the resistance of the bed material. The changes are reflected by the shape of meanders, as well, because the erosion of the banks has changed their parameters, too.

The opposite process occurs by the aggradation of the flood-plain as the embankments were built unnecessarily too far from the river. This is proved by the cross-profiles that have been taken in these areas and by the recent alluvial soil covering those flood-plains.

The flood-control measures had the effect of changing the life of the river, and altered the former flood-plains as well. The constant inundation of these latter areas ceased. The periodic floods lasted for a much shorter time and these flood-plains changed as did the natural conditions. The mineralogenic infilling came to an end as a result of the building of embankments. Only the much slower organic or biological processes operate in the area. Thus the for-mer river beds are well-preserved on these higher flood-plains. The several million hectares formerly covered by groves, moors, swamps, marshes and wet meadows became available for agricultural production. On the flood-free embankments there are about 1.5 million hectares of arable nad, 400,000 hecta-res of pastures and meadows, 80,000 hectares of vineyards and gardens, about 2000 industrial plants, 3000 km long railway lines and 4500 kilometres of public roads, fur thermore about 350,000 buildings (Figure 5-6).

In conclusion we would remark that as a result of the large-scale regula-tion of the rivers and flood-control the former separation of the country into two parts ceased. Thus the two marked regions of flood-free areas and flood-plains that divided the plains into different cultures were eliminated. Human effort with the help of the plough, eliminated in nearly 100 years the territorial differences conserved" by nature for thousands of years in the past.

Apart f rom evaluating the positive effects of river control, we must also refer to the fact that despite their successful implementation, they bear the marks of the capitalist society's approach to the problem. These faults are ma-nifested in the fact that these works only met the demands of mainly passive water management and that of the intervention needed in the given situation. The transitional climate of Hungary is characterized by 3-4 humid years, gen-erally followed by a dry period of 5-6 years. In the first case a great abun-dance of water, in the latter its shortage may reduce agricultural production.

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Fig. 4. Longitudinal profile of the Tisza before and after the regulation

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Regulated rivers 47

Fig. 5. A section of the Danube before and af ter the regulation

This climatic factor would have required the construction of irrigation canals and reservoirs, the draining of excess waters, furthermore water transport to serve production needs should also have been developed. Apart from some modest initiatives in the period between the two world wars, this could only be realized in the last quarter of the century with the financial backing of our socialist society.

The first important irrigation project was implemented on the Tisza, the Tiszalok Dam — opened in 1955 — that supplies the poorly served areas of the

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Regulated rivers 49

Fig. 6. a-b. The environs of Szeged before and af ter the river control

Koros rivers with irrigation water from the 108 km long main Eastern Irriga-tion Canal. The first dam near Bokeny on the Harmas-Koros was built in 1905, the second in 1942 near Bekesszentandras and the third near Bekes in 1969. This was followed by the opening of the Tisza II Dam near Kiskdre. All these serve as reservoirs of irrigation water improving the ship-ping possibilities in these dammed-up sections. The Tisza Dams provide a mo-dest amount of electrical eriergy. In addition, the artificial water ponds of 130 sq. km thus created by the reservoir of Kiskore will improve the recreatio-nal-sporting facilities of the poorly watered environment. The planning of the third Tisza Dam near Csongrad is already in progress. There are more impres-sive tasks to be completed on the Danube river. Namely along the section be-tween Bratislava and Gonyii about 5-8000 m3 alluvia are deposited annually in spite of all preventive efforts. This raised the river bed in the last hundred years considerably. Besides, the gradient of the river at this stage is more than 30 cm/km. The interaction between the deposited alluvium and the steep gra-dient lead to a so-called changing, shifting channel and the formation of alluvial cones. Navigation here even at a sufficient depth of water is difficult and gene-rally needs twice as much energy as that required below Gonyu. It becomes even more difficult and sometimes quite impossible during the usual autumn low-water levels. The Danube is, however, an important waterway. Despite its present limits, the amount of goods transported in 1970 was twice as much as in 1960 and rose f rom 2.5 million tons to 4.5 million tons. This increase in the

4 Geographia Polonica 41 http://rcin.org.pl

50 S. Somogyi

traffic might be explained by the fact that contrary to the arguments of the advocates of road transport, the advantage of river transport lies in its cheap-ness, i.e., with one horse-power capacity eight times as much goods can be trans-ported by ship than by train and about thirty times as much-as on public roads.

The importance of the Danube in national and international flow of goods will grow on the completion of the Danube — Main — Rhine Canal that will be opened in the 80's and it will be followed some time later by the construction of the Danube — Odra Canal now at the planning phase. These international efforts demand large-scale investment and will only be profitable if the navi-gability of the Danube is improved so that it would become a fourth-class ship-ping route, with an undisturbed flow of traffic, 1000 ton tow-boats. Apart from these possible improvements the present capacity of 7 million tons in the sec-tion between Bratislava and Gónyü cannot be increased.

These requirements can only be fulfilled by the constant artificial grading of the Hungarian section of the Danube, in order that the required depth, of channel for shipping should always be secured. For this purpose, the planning and construction of four dams is in progress :

1. Between Dunakiliti and Bos (Gabcikovo) there is a power station at the water-reservoir created by the damming up of the river.

2. There is a similar power station near Nagymaros. 3. Dams with reservoirs to be built in the near future at Adony and 4. Fajsz. Once completed these dams and reservoirs would not only form a unified

system in terms of hydraulics, navigation and water power, they would serve as an integrated system of water management and as a flood-control device. They ensure the supply of irrigation water for the nearby areas (Figure 7).

The waterways of the Danube and Tisza are supplemented by the Danu-be — Tisza Canal, which is to provide water for the southern Tisza valley, the water coming from the Danube (100 m3/s) ; furthermore it will link the shipping routes of the Danube and Tisza. We may reckon in the near and distant fu ture on the establishment of fur ther water management projects along the tr i-butaries of the Danube and the Tisza. From among these we only mention the construction of the Sió-system that compensates for the 20 cm difference in the level of the Danube and Lake Balaton with 5 locks, the first a flood-sluice-gate at the outlet — an imposing, but at the same time difficult task that requires large-scale investment by the Hungarian economy in the near future.

All these water management projects, some already completed, others still being built and planned, have and will have effects on the life of the rivers. We only mention a few of these expected changes.

1. With regard to the channel development, the following consequences are to be expected: the common after-effect of the building of dams on the Danu-be and t he Tisza wi l l r e s u l t in the movement of the water slowing down. One must therefore reckon with a greater deposition of sediments moved by salta-tion and of suspended load in the river section behind the dams. The situation in the Upper Danube will change in as far as the present deposition in the whole section will take place in the reservoir behind the dam at Dunakiliti, and from where it can easily be removed. Below the dam, the rivers will be relati-vely poor in load and the river may cut into its bed to some extent, in both the natural and artificial channels and in the former bed now used only to drain flood-waters. These sections must be protected against unfavourable bed erosion.

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F i g . 7b. D r a f t of t h e e s t a b l i s h m e n t s of w a t e r m a n a g e m e n t in t h e T i s z a - v a l l e y ( F r o m Vízügyi Kôzlemények, 2, 1974).

1 — dam already in existence; 2 — dam planned; 3 — reservoir already in existence; 4 — re-servoir planned; 5 — canal already completed; 6 — canal planned

Fig . 7a. D r a f t of t h e d a m - s y s t e m a t G a b ö i k o v o — N a g y m a r o s ( F r o m Vizügyi Közlemenyek, 2, 1974)

1 — reservoir near Dunakiliti; 2 — dam near Dunakiliti; 3 — canal for industrial water; 4 — dam, power station and lock-sill near Gaböikovo; 5 — dredging and regulation of the river bed;

6 — dam, power station and lock-sill near Nagymaros

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52 S. Somogyi

The waters of the upper sections of the Danube deprived of their deposits, can no longer move a significant amount of alluvium neither at the Nagyma-ros nor at the Adony revervoir, one above the other below Budapest.

The planned Danube — Tisza Canal would pass through rather loose sedi-ments. The movement of water flowing along and the backwash caused by the ships would lead to bank erosion and to considerable aggradation if it were not prevented artificially.

The Tisza transports only suspended load but this is a greater load than that of the Danube if we compare the capacity of both rivers. Nevertheless, one does not have to reckon with a more significant aggradation because the slower movement of water reduces channel erosion. The only areas where aggradation may be a problem is the section of the Tisza below the outlet of the Sajo and the Maros; both tributaries carry rich alluvia into the Tisza. The situation at the outlet of the Maros is fur ther complicated by the construction of a dam in Yugoslavia near Nowi' Becej (tJjbecse).

A general consequence of the slowing down of water movement is that the changes in the river-bed will take a much longer time than they do at present.

2. Changes in the seasons of navigation. At present river traffic is consid-erably hindered by periodic lack of adequate conditions for navigation, e.g., very low water levels. The water reservoirs and the dams eliminate fords and thus intervals of no navigation will be limited to icy winter periods.

The breaking-up and drifting of ice in winter will start ealier behind the dams, similarly the freezing of the ice also unless it is artificially prevented. Thus, though the period of navigation is prolonged the ice may prove to be a problem in winter. Incidental icy floods can be controlled by the operation of sluice-gates at the dams and thus their danger and frequency can be limited. The more balanced water regime due mainly to\the dams and channels acce-lerates river traffic upstream only, i.e., behind the dams it is a significant time factor. This is complemented by the night traffic in the smoother section, and the introduction of modern communication and navigation techniques. These improvements add up to nearly 40% extra navigation-time.

3. Effects on water quality to be expected. The occupational regrouping of the population and industrial development along the rivers, the use of chemi-cals in agriculture in the cultivation of the riverside areas led to the deteriora-tion of the quality of the water. We must also add the pollution caused by water traffic. The construction of the transcontinental shipping routes means that the rivers in Hungary may now be termed to belong to the category of big lakes, where there is no self-purification by natural water movement, and with the increased traffic the danger of pollution becomes more imminent. Protection against pollution would not be sufficient even if all waste and used water that enters the river in Hungary is completely purified since Hungary occupies only one quarter of the total (titel) catchment area of Danube and cannot carry the burdens of the other three quarters of the catchment area. In this respect only effective international co-operation would be of help.

Sources of imminent danger of pollution in the Upper Danube section are the oil-products coming from abroad, the waste waters of Budapest entering before Adony, the waste waters of the industrial plants and suburbs of South-ern Pest, flowing into the Danube — Tisza Canal. Entering the Kiskore Reser-voir the waste waters of the Sajovalley and Leninvaros and above the Novi Becej Reservoir the waste waters of Szeged are discharged. It is a fundamental requirement that as the channelling of the river progresses, plants for purifying

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Regulated rivers 53

t hese w a t e r s should be bu i l t a longs ide so t h a t t h e absence of r e d u c e d s e l f - p u -r i f y i n g e f f ec t s should no t cause i r r e d e e m a b l e d a m a g e s in t h e q u a l i t y of w a t e r .

T h e f u r t h e r e f f e c t i v e p l a n n e d social i n t e r v e n t i o n in t h e l i fe of t h e H u n g a -r i a n r i v e r s wi l l n a t u r a l l y h a v e seve ra l o the r consequences . T h e soil w a t e r b a -lance a long t h e r i v e r s ide wi l l be r ad ica l ly c h a n g e d so wi l l t h e p r e s e n t vege -t a t i o n a l cover of the f lood-p la ins as t h e a r t i f i c i a l l ake p a r t l y i n u n d a t e s these p la ins , a n d t h e d y n a m i c s of soil d e v e l o p m e n t a r e a l t e red bo th w i t h i n a n d ou t -side t he n e w e m b a n k m e n t s ; local c l imat ic changes a r e also to be e x p e c t e d n e a r t h e r e se rvo i r s . A t p re sen t , w e m e r e l y r e f e r to these expec t ed c h a n g e s as t h e f u t u r e e x a m p l e s of the in t ens ive p r e s e n t - d a y i n t e r v e n t i o n s in t h e l i fe of r i ve r s in H u n g a r y .

REFERENCES

Babos, Z., Mayer, L., 1939, Az ármentesítések, belvízrendezések és lecsapolások f e j -lodése Magyarországon (The development of flood-control and inland-water drainage in Hungary), Vízügyi Közlöny, 32-91, pp. 225-287.

Bulla, B., 1962, Magyarország természeti földrajza (Physical geography of Hungary), Budapest, Tankonyvkiadó.

Károlyi, Zs., 1961, A Tisza mederváltozásai (Changes in the r iver-channel of the Ti-sza), Budapest, Vizgazdálkodási Tudományos Kutató Intézet, Tanulmányok és Kutatási Eredmények, 8, 1. •

Károlyi, Zs., 1960, A vízhasznosítás, vízépítés és vízgazdálkodás torténete Magyaror-szágon (History of the utilization of water resources and water management in Hungary), Budapest. Müszaki Egy. Közp. Konyvtára. Müszaki Tud. tör t- i Kiadvu 13.

Lászlóffy, W., 1932, A Tisza-völgy. (Valley of the Tisza river), Vízügyi Közl., 2, pp. 108-142.

Lászlóffy, W., 1934, A magyar Duna vízjárása (Water regime of the Danube river), Vízügyi Közl., 1, pp. 39-64.

Lászlóffy, W., Csermák, B., 1958, Budapest és kornyékének vízrajza (Hydrography of Budapest and its environs), Budapest, i n : Budapest természeti képe, pp. 427-471.

Pécsi, M., 1959, A magyarországi Duna-völgy kialakulása és felszinalaktana (Forma-tion and morphology of the Hungarian Danube valley), Budapest, Akadémiai Kiadó.

Schmidt, E., 1929, A. vízszabályozás fejlodése és jelen állása Magyarországon (The present state and development of water regulation in Hungary), Vízügyi Közl., pp. 1-92.

Somogyi, S., 1961. Hazánk folyócházatának fejlodéstorténeti vázlata (History of the development of the drainage network in Hungary), Földr. Közl., 1, pp. 25-50.

Szablocs, L., 1961. A vízrendezések és az öntözesek hatása a tiszántuli talajképzodési folyamatokra (The effect of water management and irrigation on soil forming processes east of the Tisza river), Budapest, Akadémiai Kiadó.

Tory, K., 1952, A Duna szabályozása (Regulation of the Danube), Budapest, Akadémiai Kiadó.

Vujevic, P., 1906, Die Theiss, Leipzig. Geogr. Abhandlungen, 7, 4, pp. 1-76. Tanulmányok a Duna — Rajna és a Duna — Tisza csatornák megépitésének magyar-

országi területfejlesztési hatásairól (The effect of the Danube — Rhine and Da-n u b e — Tisza channel on regional development in Hungary), Budapest, 1972-1974, MTA FKI (manuscript).

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GEOGRAPHIA POLONICA 41, 1979

P O T E N T I A L F O R C H A N G E I N T H E W A T E R C Y C L E O N C U L T I V A T E D S L O P E S

JANUARY SLUPIK

Institute of Geography and Spatial Organization, Polish Academy of Sciences, Cracow

1. INTRODUCTION

1.1. SCOPE OF WORK

Land use is one of the important factors which differentiate both the quan-titative and qualitative water cycle structures in the soil. The term land use refers to the spatial arrangement of both vegetation cover and the agricultural activities of man. The knowledge of relationships between soil water cycle and land use makes it possible to determine the impact of man on the water cycle and to control the soil water cycle by rational land use.

The above problem is discussed by taking as example the results of conti-nuous measurements at Szymbark in the flysch Carpathians. The study area is situated on the boundary of two major relief types: the Carpathian Foothills and the Beskidy Mts. (Beskid Niski, L. Starkel, 1973). In the Foothill region, slopes consist of flysch series with prevailing shales on which loamy soils have developed. Slopes are occupied by cultivated land. The forested Beskidian slopes are mostly made up of flysch sandstone and have loamy soils with high frequencies of skeletal particles. Forests are still in their natural state there (J. Staszkiewicz, 1973).

1.2. NATURE OF THE WATER CYCLE ON FORESTED AND DEFORESTED SLOPES

Comparison of the water balance on forested and deforested slopes reveals the extent and trends of changes caused by the removal of forest cover in earlier centuries. It appears that the percentage share of infiltration in the open is similar to that under forest (Table 1) because of high rainfall intercep-tion by forest. Differences in the runoff processes are essential. The maximum intensity of surface runoff on a wooded slope is 50-times smaller than that

TABLE 1. Water balance in forest and in cultivated areas at Szymbark — percentage comparison

Area Precipitation Interception, depression storage

Surface runoff

Infiltration

Forest Cultivated areas

100 100

20-25" 5-20"

0-5 5-20

70-80 60-90

" according to K. Dçbski (19 70)

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56 J. Słupik

TABLE 2. Maximum intensity of runoff expressed in 1/min- ha in forest and in cultivated areas at Szymbark (according to E. Gil)

Maximum intensity Area

overland flow throughflow and interflow

Forest 150 160 Cultivated area 8,250 190

on cultivated slopes (Table 2). The intensity of subsurface runoff in the 1 m slope mantle is smaller. This can be explained by the similarity of the deeper soil horizons under forest and in the open (B. Adamczyk and co-workers, 1973).

The above hydrological differences are only in part due to the influence of forest. It should be remembered that the forest cover has mostly been re-moved from areas useful for agriculture. Forest was left on slopes containing skeletal soils, unsuitable for cultivation. Thus, numerous environmental factors are responsible for the varied water cycle in woodland and in the open. Struc-ture of the soil profile and lithology of bedrock are of major importance. Such are the varied natural conditions on the experimental slopes at Szymbark (Table 3). It may be assumed that the reforestation of the cultivated slopes would not be effective from the hydrological point of view.

TABLE 3. Natural conditions of the experimental slopes "Jelenia" and "IG PAN" at Szymbark

Elements "Jelenia" "IG PAN"

Lithology sandstones shales/sandstones Soil skeletal silty-loam silty loam

total porosity in % of volume 46.1-60.2 40.7-51.2 capillary porosity in % of volume 36.8-53.4 33.3-42.5 infiltration in mm/min 0.8-42.9 0.07-11.4

Vegetation Forest: Dentario cropland /grassland glandulosae Fagetum

Slope profile straight straight Slope and exposure 19°, NE 12°, S W Altitude in m a.s.l. 550-650 300-350 Annual precipitation in mm (1969) 715 670 Mean annual min. and max. temperature in °C 3.1-9.5" 1.8-12.0"

" according to B. Obrębska-Starklowa (1973)

1.3. N A T U R E O F T H E E X P E R I M E N T A L S L O P E S

The experimental slopes at Szymbark represent different natural conditions (Table 3). The slope "Jelenia" representative of the wooded Beskidian slopes is composed of the Magura sandstone series. It is situated in the lower mount-ain zone (regiel dolny). The "IG PAN" slope representative of the cultivated Foothill slopes is formed of shales and sandstones belonging to the Inoceramus strata. It was the aim of continuous measurements to find out the mechanism of change from precipitation to runoff. This phase in the water cycle takes

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Change in water cycle 57

place on the slope. The measurements of each of the elements in the water cycle were made on the "IG PAN" slope. These included: precipitation, water infiltration and percolation, surface runoff (overland flow), subsurface runoff (troughflow and interflow), soil moisture content and oscillations of the ground-water level (J. Slupik, 1973).

2. THE HYDROLOGICAL ROLE OF LAND UTILIZATION

2.1. THE PROBLEM

The utilization of cultivated areas varies with the seasons of the year. At the same time weather is changing. Knowledge of the hydrological role of land use involves analysis of the water cycle during different weather. The results of measurement at Szymbark demonstrated that different types of weather — each characterized by a distinct set of hydrological processes — can be distinguished. Downpours of short duration, long-lasting continuous rains and snowmelts are typified by the increased activity of runoff processes. Du-ring the other rains either infiltration or interception is predominant. In the rainless periods of the summer season (from May to October) évapotranspira-tion prevails. During the frosty periods hydrological processes disappear. The causative relationships between soil water cycle and land use vary with the weather (E. Gil and J. Slupik, 1972a, 1972b; J. Slupik, 1972, 1973, 1974; J. Slu-pik and E. Gil 1974).

2.2. NATURE OF THE SOIL WATER CYCLE VARYING WITH THE WEATHER

During the summer drought dessication of the soil takes place due to the intense évapotranspiration. In spite of the warm weather (daily mean air tem-perature of 17.2 °C, maximal air temperature of 31 °C, maximal temperature of ground surface of 51 °C), after 20 rainless days some 80 mm of water avai-lable for plants have been recorded in the 0.5 m soil layer (Fig. 1). The level of cultural plants was very good then. The conclusion is that the loamy soils on the flysch slopes have water in excess of that needed by plants, even at the height of the growing season. There exist possibilities of increasing water con-sumption rates in the process of évapotranspiration.

In the rainy periods and during thaws, the role of land utilisation is redu-ced to that of controlling the quantitative proportions of surface retention,

Fig. 1. Changes in soil moisture on the "IG PAN" slope at Szymbark during drought 1 — soil moisture in the upper par t of slope, 2 — soil moisture in the lower part of slope,

3 — maximum soil temperature

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58 J. Słupik

surface runoff and infiltration. As the depth increases the influence of plants is reduced. The rates of both percolation and subsurface runoff are similar under various cultural plants (J. Slupik, 1974). These rates are closely related to the nature of the ground. For this reason, we can concentrate our attention on the variety of overland flow.

During short downpours both volume and intensity of surface runoff is controlled by the vegetation cover (Table 4). As a result, on the grass-covered slope water retention in the soil was 86% of the total precipitation and that on the potato field was 55%. This great variation in overland flow can be explained by the well known principles of runoff hydraulics. According to L. Schiff (1951), as the vegetation cover density increases, the ground rough-ness will be increased. This means that the surface retention necessary to initiate water flow in grassland must constitute a thicker layer of water, where-as smaller quantities of excess rainwater are quite sufficient to initiate run-off on the bare soils. During rainfall with an intensity of 1.74 mm per mi-ute on the grass-covered slope surface runoff commenced afer 34 minutes since beginning of rainfall. Thus, it may happen that when downpours are short no surface runoff will occur neither on grass-covered slopes nor on corn fields. With the same surface retention, the velocity of overland flow-declines as density of vegetation cover increases (L. Schiff, 1951): on the grass--covered slopes the velocity of water flow is 2 cm/s, on the bare soil it reaches 1 m/s (K. Figula, 1960). Compared to grass and corn, the velocity of surface runoff is much greater under root crops. This is the cause of increased runoff intensities (Table 4).

TABLE 4. Surface runoff on the "IG PAN" slope during short storm rainfall

Elements grass potatoes

Precipitation total in mm 43.2 43.2 Maximum rain intensity in mm/min 1.74 1.74 Rate of surface runoff in mm 0.0 10.2 Maximum runoff intensity in 1/min • ha 17 3,400

During downpours land utilization permits both volume and velocity of overland flow to be controlled directly. The maximum difference in runoff rates is equivalent to a layer of water 7.4-10.2 mm thick during downpours above 40 mm in 30-40 minutes. In Poland such downpours are rare (J. Lambor, 1971). This 10 mm difference gives the upper limiting value of the influence of vegetation. This value applies to the cultivated Carpathian slopes containing loamy soils. Continuous rains (lasting a few days) of high precipitation totals may be above 100 mm (T. Nedzwiedz, 1972). The amount of falls exceeds the soil water capacity leading either to surface or subsurface runoff of excess water. The magnitude of both types of runoff depends on the proportions of precipitation totals and capillary water capacity of the ground. The runoff volume is determined by the structure of the ground and not by the utilization of land (J. Slupik, 1973). Similar rate of surface runoff has been recorded in all cultivated areas (Table 5). The influence of the vegetation cover is mani-fested only in the intensity of overland flow. The latter will be reduced as the

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Change in water cycle 59

density of the plant cover is increased (Table 5). Thus, possible changes in the water cycle during continuous rain should be limited to the control of runoff velocity.

The remaining rain types include: (a) rains with totals not surpassing the actual soil water reserve, and (b) rains with intensities not exceeding the rate of water infiltration. Those rains may cause surface runoff only in furrows and on field- and forest roads. On the fields such rains are favourable for the wa-ter storage in the soil. Overland flow and percolation are minimal then and subsurface runoff does not occur (J. Slupik, 1973, 1974).

TABLE 5. Surface runoff on the "IG PAN" slope during continuous rain of 4 days' duration

Elements grass potatoes

Precipitation total in mm 167.2 167.2 Amount of surface runoff in mm 25.3 23.4 Runoff coefficient in % 15.1 14.0 Maximum intensity of flow in 1/min • ha 765 848

The flow of water on the slopes is accelerated and concentrated by field-and forest roads, and by furrows as well (E. Figula, 1960). These are charac-terized by low permeabilities and the absence of vegetation, and they drain water from the soil layer. Measurement at Szymbark revealed that the volu-mes of water using a furrow 130 m long and draining a field of 130 X 13 m are similar (Photo 1). The water flow velocity in a furrow was exceeded some ten-

Photo 1. Measurement of overland flow in a fu r row on the "IG PAN" slope

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60 J. Słupik

Photo 2. Furrows and field roads make a very high drainage density on slopes (surroundings of Szymbark)

fold (above 1 m/s) (K. Figula, 1960). The density of both furrows and field roads at Szymbark is about 50 km/km2 (Photo 2). For this reason I am of the opinion that furrows, field- and forest roads are the main source area of water supplied from the slopes into the stream channels during high discharges. The high velo-city of water draining the network of furrows and roads determines essentially the peak flows in the small Carpathian catchments. During downpours, \furrows and roads also add to the volume of water flowing downhill into the stream channels. The conclusion is that by reducing the number of furrows and roads runoff velocity can be much reduced. The same applies to the volume of over-land flow that takes place on the slopes during downpours.

During thaws (snowmelts) the soil moisture content is high. Most frequently it approximates to the full soil water capacity (J. Slupik, 1974). Thus, condi-tions are similar to those prevailing during continuous rain. The magnitude of overland flow is determined by the state of the ground.

In the winter season (November-March) the major role is played by ground temperatures (Table 6). The influence of land use is that of differentiating

TABLE 6. Surface runoff on the "IG PAN" slope during snowmelts in different soil conditions

frozen soil not frozen soil Elements

grass-covered ploughed grass-covered ploughed

Amount of surface runoff in mm 27.5 Runoff coefficient in % 77.9 Max. intensity of flow in 1/min • ha 195 %

21.5 3.8 0.1 60.7 5.0 0.1

170 , 35 12

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Change in water cycle 61

the runoff velocity. Some changes in the runoff volume may be estimated by increasing the surface retention of the ploughed fields. Compared to a grass--covered slope, the decrease in runoff volume on a ploughed field is distinct and independent of the then prevailing state of the ground (Table 6). However, variation in overland flow volume is compensated by higher subsurface runoff rates on the ploughed field. Throughflow occurs chiefly in the arable layer (J. Slupik, 1972b; E. Gil).

The possibility of changes in the water cycle is limited to the control of flow velocity. Lower velocities have been observed on the ploughed fields (the furrows due to ploughing are ignored). For this reason, the hydrologic effects may be greatest, if the number of both furrows and field roads had been redu-ced. This method is likely to decrease runoff velocities during snowmelts and in rainy periods.

3. CONCLUSIONS

Both type and method of land cultivation has a direct bearing on .the runoff velocity and a partial influence upon the overland flow volume. Runoff condi-tions may be improved in two ways: by increasing runoff volume and accele-rating the downhill flow, or reducing both the volume and velocity of over-land flow. On the Carpathian slopes, the decreased runoff velocites will increase periodically the water retention in the soil. It also will diminish the rates of soil erosion. This will lead to excessive soil moisture being disadvantageous for two reasons: firstly, the growth of plants will be limited; secondly, condi-tions will be favourable for landslide initiation. Agricultural production ne-cessitates increase (or acceleration) of the water flow during wet periods, when runoff volume and velocity should be reduced in order to protect the soil from erosion. A complex discussion of changes needed in the water cycle on the flysch Carpathian slopes is contained in another paper.

The effects of changes in the water cycle structure that have been caused by the utlization of land do not pertain only to slopes. As the runoff velocities on the slopes are decreased the peak flows in small catchments are reduced. Thus the danger of both flooding and channel erosion will be reduced in areas extending above the dams. The control of water flow velocities on the slopes is the only way to reduce the effects of floods in the small catchments. As far as larger drainage basins are concerned the control of the downhill flow of water is less effective. Floods are produced only by continuous rains there, when the runoff volume does not depend upon land utlization. The peak flows are governed by the different lengths of time the water needs to come from the small catchments (J. Lambor, 1971). Reservoir construction is the only way to diminish the effects of floods on the Carpathian tributaries to the Vistula river.

REFERENCES

Adamczyk, B., Maciaszek, W., Januszek, K., 1973, Gleby gromady Szymbark i ich wartość użytkowa (Sum.: The soils of village group Szymbark and their utility value), Dokumentacja Geograficzna, 1, pp. 15-72.

Dębski, K., 1970, Hydrologia (Hydrology), Warszawa. Figula, K., 1960, Erozja w terenach górskich (Sum.: Erosion in highland regions),

Wiadomości IMUZ, 1, 4, pp. 109-147.

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62 J. Słupik

Gil, E., Słupik, J., 1972a, The influence of the plant cover and land use on the surface run-off and wash-down during heavy rain, Studia Geomorph. Carpatho-Bal-canica, 6, pp. 181-190.

Gil, E., Słupik, J., 1972b, Hydroclimatic conditions of slope wash during snow melt in the flysch Carpathians, Les Congres et Colloques de L'Universite de Liege, 67, pp. 75-90.

Lambor, J., 1971, Hydrologia, inżynierska (Engineering hydrology), Warszawa. Niedźwiedź, T., 1972, Heavy rainfall in the Polish Carpathians during the flood in

July 1970, Studia Geomorph. Carpatho-Balcanica, 6, pp. 194-199. Obrębska-Starklowa, B., 1973, Stosunki mezo- i mikroklimatyczne Szymbarku (Sum.:

Meso- and microclimatic conditions at Szymbark), Dokumentacja Geograficz-na, 5.

Schiff, L., 1951, Surface retention, rate of run-off , land use, and erosion relation-ships on small watersheds, Tans. AGU, 32, 1, pp. 57-65.

Słupik, J., 1972, Spływ powierzchniowy na stokach górskich Karpat fliszowych (Sur-face run-off on slopes in Flysch Carpathians), Gospodarka Wodna, 8.

Słupik, J., 1973, Zróżnicowanie spływu powierzchniowego na fliszowych stokach górskich (Sum.: Differentiation of the surface run-off on flysch mountain slo-pes), Dokumentacja Geograficzna, 2.

Słupik, J., 1974, Der Wasserkreislauf in Bóden an den Hangen der Flyschkarpa-ten — dargestellt an Beispielen aus der Umgebung von Szymbark, Beitrage zur Hydrologie, 2, pp. 67-84, Freiburg.

Słupik, J., Gil, E., 1974, The influence of intensity and duration of rain on water circulation and the ra te of slope-wash in the flysch Carpathians, Abhandlungen der Akademie der Wissenschaften in Góttingen, III. Folgę, 29, pp. 386-402.

Starkel, L., 1973, Cel i zakres studiów nad środowiskiem geograficznym okolic Szym-barku (Sum.: Introduction — aim and scope of investigations on the geographical environment of the region of Szymbark), Dokumentacja Geograficzna, 1, pp. 7-14.

Staszkiewicz, J., 1973, Zbiorowiska leśne okolic Szymbarku [Beskid Niski] (Sum.: Forest communities of the vicinity of Szymbark, Low Beskid), Dokumentacja Geograficzna, 1, pp. 73-97.

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GEOGRAPHIA POLONICA 41, 1979

T H E S I L T I N G P R O C E S S E S O F T H E A R T I F I C I A L W A T E R R E S E R V O I R S I N T H E P O L I S H L O W L A N D

KAZIMIERZ WIĘCKOWSKI

Institute of Geography and Spatial Organization, Polish Academy of Sciences, Warsaw

In Poland as well as in many other countries one of the fundamental de-mands for fur ther economic progress is effective safeguarding of water resour-ces of suitable quality and quantity to cover present and future requirements of population, agriculture and industry.

In view of this necessity it is planned to construct in Poland a number of additional reservoirs, many of these — and mainly the largest among them — are going to be built on rivers in Poland's Lowland. In the design of such re-servoirs an essential factor is due calculation of how long they will be of use because this consideration of the economic aspect of building the reservoirs and of the nature and extent of their fur ther use, involves also a wide range of later auxiliary investments. In the desigh plans this sort of prognosis is made by different, mostly indirect, methods and, most often, they are based on calculations of the intensity of surface washdown (denudation) and erosion, and of bank abrasion in river valleys lying within the range of the fu ture catchments area.

However, from numerous instances witnessed during recent decades and in many countries of the World — especially in the USA and the Soviet Union — it is well known that this sort of preliminary theoretical calculation of the intensity of possible silting of new water reservoirs has proved to be fallacious in many instances. It is a fact that artificial reservoirs whose period of usefulness had been believed to last hundreds of years or, at any rate, long periods, have been completely silted up within a dozen years or less, resulting in heavy economic losses.

This is why work on improving methods for preparing forecasts of the life of new reservoirs continues. Among other things, these efforts are to be sup-ported by investigations into the rates at which existing water reservoirs are being silted up, because any observations of the results obtained in this way may considerably improve the accuracy of such preliminary, rather theore-tical forecasts of the life of reservoirs which are to be made under conditions resembling those of present-day physico-geographical, and particularly, of lo-cally determined geological-lithological and hydrographic conditions.

Obviously, a detailed description of all these investigations would far exceed the framework of the presfent study. Hence the author decided to give merely a brief survey of the method so far applied in Poland in this sort of examination of the rates at which existing reservoirs are being silted up, and of the assumptions used in anticipating rates of silting up of such newly con-structed reservoirs.

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64 K. Więckowski

Most often this rate is estimated from the intensity of denudation, i.e. from processes of surface soilwash (Reniger, 1959) observed within the drainage area in question and expressed by what Dębski (1959) called the "index of denu-dation", in values of t/km2/y. Variations on this method are direct measure-ments of the material eroded and carried off, expressed in g/m3 of water for material floating in or dragged along a river bottom, or in tons or m8/y, when this material is brought into the reservoir from the catchment area (Brański, 1966, 1968; Cyberski, 1969; Mikulski and Chomiak, 1963; Wiśniewski, 1969). In both instances mentioned above there must also be calculated the "reservoir capacity of retaining the material supplied", expressed in a percentage of the total quantity of material supplied by the river; usually this figure varies widely, from 40% to 95% (Wiśniewski, 1966, 1970 a,b).

It should also be mentioned that in some cases periodic measurements were made of the changing depth of the reservoirs caused by silting. Such measure-ments were made either by classical methods at a great number of points, or by continuous so-called echo-sounding along definite fixed cross-sections (Ba-siński, 1964 a, b; Onoszko, 1962, 1964; Wiśniewski, 1963). The thickness of the bottom deposits used to be determined either from knowing original depths at points of particular cross-sections, or from measurements repeated every few years. In both cases the amount of silting used to be recorded in millions of m3/y, or in figures indicating the annual increase or loss in thickness of the previously determined bottom deposits (Wiśniewski, 1970 a, b).'

However, the results obtained from all the above methods proved to be rather inaccurate, especially when the "coefficient of denudation" has been chosen very arbitrarily. The results were only a little more accurate by meas-uring the material floating in or dragged along by the river ,mainly due to difficulties in measuring at all during flood periods). Nor can it be considered any more reliable to give data stating the capacity of a reservoir, i.e. how much of the impounded material it can retain.

As well as this, and usually omitted in all these calculations was the autoch-thonic, mainly organic material which accumulates in the bottom of storage reservoirs in consequence of biological processes; yet the share of this ma-terial in the silting up of some reservoirs can be considerable.

When the silting up of storage reservoirs is measured by checking their reduced depths the results may also be rather unreliable, no matter whether they were obtained by the classical method or by echo-sounding. The reason is, that very often — down to some 30 or 50 cm depth — the top layer of the bot-tom deposits, especially when containing larger quantities of organic material, is a soft, even semiliquid mass. Here the basic difficulty, so far practically unsolved, lies in establishing the true depth revealed by echo-sounding, or the true depth to which the weighing element of a classical sounding device pe-netrates the soft top layer of the deposit. Inaccuracy of the apparatus used may also have to be taken into account (in the case of echo-sounding) and errors may be caused by wave action.

Considering all the difficulties involved, the author of the present report tried to determine by means of core sampling the rates at which reservoirs lose their retentiveness followed by measurements of solid cores extracted from the bottom deposits. They illustrated in vertical columns the structures of the bottom deposits in a downward direction, from water-sediment surface to the bedrock (say, to a submerged meadow). In order to obtain and extract this sort of solid core from the bottom deposits, the author applied a core sampler of his own design (Więckowski, 1970). From 1958 onwards this device was used successfully in Poland in comprehensive investigations of the bottom deposits

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The silting processes 65

of many natural lakes and, moreover, in determining the rates at which these lakes are being silted up (K. Więckowski, 1968).

In wintertime the job of depth sampling is done from the ice surface, at points accurately marked along geodetically marked series of cross-sections or at points of a uniform network of squares. During the summer, sampling is done from a floating platform (of the catamaran type), and the cross-sections are laid down from marking poles set up on opposite lake banks. The distances between particular sampling points sounding are either established by optical range-finders, by triangular interaction, or by using a measuring tape with one end attached to the bank.

The method of determining the rate of silting up, resulting from direct thickness measurements of bottom deposits as has been described in detail before, has also been applied at two artificial water reservoirs situated in the Polish Lowland: at Zegrze on the Narew and at Włocławek on the Vistula rivers.

The Zegrze Reservoir (Zbiornik Zegrzyński), built in 1962, has a surface area of 33 km2 and a lenght of approximately 18 km. This reservoir may be di-vided into 3 parts differing in shape and in hydrodynamic regime as follows: a lower, relatively narrow (about 600-800 m) and almost straight part some 8 km long, a middle part about 5 km long and up to 3 km wide forming what is called the deep basin, and an upper part, very narrow and 4 km long.

During our field studies carried out all over the area of thiś reservoir, corings were made along 20 transverse sections (at 1 km intervals)) to deter-mine the thickness of the bottom deposits in 360 points and to collect from 100 points samples to be analyzed in the laboratory.

Simultaneously observations were made for defining the hydrodynamical regime in particular parts and zones of the reservoir, depending on the shape of the reservoir and the relie'f of its bottom. Most important in this case was the determination of the different velocities of the water, because they effect the type of bottom deposits laid down and the rate at which these deposits accumulate.

It appeared that not only in the former channel of the Narew river but also outside the channel in the areas which are now inundated, the hydrody-namical regime of water resembles much more that of a river than a lake. Evidence for this is the lack of vertical thermal stratification of water layers so characteristic of most lakes; also characteristic are the periods in which a complete water exchange in the reservoir takes place. It was found that, even when river outflow had dropped its next to lowest values, a complete renewal of water in the reservoir averaged 14 to 16 days, whereas for flow vo-lumes approaching mean long term values a full exchange takes place every 4 to 6 days; during flood periods this even happens every 12 to 24 hours. Hence the Zegrze Reservoir can by no means be classified as one marked by a "de-layed water exchange" — this being one of the main features characterizing the hydrodynamical regime of lakes, including drainage lakes.

Our reasoning is also confirmed by the results of hydrobiological exami-nations (Dojlido et al., 1967), from which their authors conclude that "from the viewpoint of both their chemical composition and their biocenosis the wa-ters of the rivers Bug nad Narew revealed but minor changes being after ponded up; hence it seems that ostensibly the lacustrine features only faintly observed in the Zegrze Reservoir are typical of this kind of lowland storage reservoir. It should be added here that these "faintly observed lacustrine feat-ures" were identified by the authors merely in the area of the wide "deep"

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66 K. Więckowski

part of the reservoirs, conspicuous by the greatest stability of its water masses.

Investigations have demonstrated that, due to the rapid flow within the former Narew channel, some 150 to 300 m wide and extending nearest the high right-hand lake shore, no material brought into the lake in suspension is being deposited; and that there is merely accumulation of some fine- and very fine-grained sand dragged in along the channel bottom.

On the other hand, all over the wide area that became submerged af ter pondage, deposits were being laid down consisting of dark green or, mostly, dark brown clayey mud with a considerable admixture of organic detritus, for the most part remmants of flora and fauna growing within the reservoirs. How-ever, this content of organic substances averaging some 10°/» in volume shows spatially wide differences, from l-2°/o to 20%; similar discrepancies lacking any sort of uniformity show also the degree of sand admixture these deposits contain. It seems clear what is to blame: all over the lake surface sand is being scooped up and dredged most of the time; it is then transferred to the shore where it is used for smoothing beach surfaces, levelling bank lines and filling in unwanted depressions. All this work is done on a fairly large scale, so that now this continuous removal and transfer of material f rom the lake bottom leads here and there to widespread areas of excavations and uneven heaps of material. Because this practice causes constant relief changes in the lake bot-tom, in sum total these endeavours greatly obstruct a clear vision of the spatial differences developing in the intensity of accumulation and in the very cha-racter of the bottom deposits.

Resuming our description of the bottom deposits it should be added that they contain a bare 3 to 5°/o CaCOs, due mainly to the plentiful occurrence of broken shells of Dreisensia Polimorpha in the reservoir. The consistency of the deposits changes gradually, from semiliquid in the top to compact in the bottom layers; the specific gravity, correspondingly changes from 1.1 to 1.8 g/cm3. In the size classification of the mineral part, fine-grained sand and silt fractions predominate while the share of clayey fractions is small, only from 2 to 5%.

By reason of the large number of samplings made it was possible, after all, in spite of the above described difficulties, to determine fairly accurately the differences in how much bottom deposits have accumulated in particular parts and zones of the reservoir. It was found that bottom accumulation of the depo-sits proceeds slowest in the lower part of the reservoir, with their thickness ranging from 0 to 20 cm, and 10 cm on the average. These deposits are dark brown mud with a low content of organic material, but are fairly strongly mixed with sand.

Sedimentation is more prounced in the middle part of the reservoir — mainly due to much slower water flow within this widest part of the reser-voir. Here the deposits are from 0 to 40 cm thick, averaging 15 cm. These depo-sits resemble those mentioned before, but contain more organic substances and usually less sand.

Finally, in the upper part of the reservoir the deposits are from 10 to 60 cm thick, again averaging 15 cm; they are much diversified with regard to the or-ganic substances content and sand admixture. In stratification thin mud layers often alternate here with beds of fine- and mediumgrained sands. This diver-sity of the deposits is caused by the wide varieties occurring here in flow rate and flow volume during periods of low water and of floods.

An analysis of all our measurements indicates that, on the average, the thickness of the bottom deposits grows annually 0.5 cm in the lower part of

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the basin and 1.0 cm in the middle and the upper part. In view of the fact that the mean depth of the particular parts of the basin differs, the Zegrze Reser-voir is bound to lose its retentive value by degrees. Realizing that due to na-tural processes the intial thickness of the bottom deposits is going to grow sons it was impossible to take into account phenomena and processes which deposits the reservoir will have lost its usefulness and its faculty of retaining surplus water, calculations reveal that for the lower part of the reservoir the total silting up is going to occur after some 600 to 800 years, for the middle part after some 450 to 550 years, and after 300 to 400 years for the upper part of the reservoir.

However, this estimate is merely an approximation, because for other rea-sons it was impossible to take into account phenomena and processes which in future may essentially change, periodically or continuously, the conditions and the rate of silting.

The Włocławek Reservoir (70 km2) extends between Włocławek and Płock, forming a fairly narrow (only 1-2 km wide) and practically straight band of water storage. The eastern bank of this reservoir is almost identical with the former Vistula bank, while the left-hand (western) bank consists alternatively of sections of an earth dam piled up on the flood or overflood terraces, and of fragments of the natural fairly high margin of the Vistula valley

The nature and scope of studies concerned with the reservoir site — cover-ing only the lower part of the basin, up to some 20 km in upstream direction — resemble what was done in the Zegrze Reservoir. Along 10 transverse cross-sections 160 soundings were made, combined with extraction of cores of the bottom deposits in order to measure the thicknesses of the deposits and to collect samples for laboratory examinations. Also studied was the flow regime within the basin. It appeared that this regime resembles very much what has been determined for the Zegrze Reservoir, both as regards differences in flow velocity in the transverse sections and as regards a complete water exchange under particular conditions of unit flow during the year.

Our investigations indicated that within the reservoir the bottom deposits are mostly laid down in a fortuitous manner. Even so, the differences in the rate of deposit accumulation show some regularities, depending on present-day flow conditions as well as on the original relief of the bottom of the reservoir.

It came to light, that next to the high right-hand bank which is suffering heavy destruction by abrasion causing huge landslides, in a zone 30 to 50 m wide new deposits were constantly being accumulated from what had been carried off from destroyed banks. The thickness of these deposits may be as much as 70 cm and its average thickness some 30 do 40 cm. Nearest the bank this material consists first of medium- and fine-grained dark sands and, far ther off, of slightly clayey dark silts; this material contains a bare 1 to 2% of organic substances; its specific gravity is 1.6 to 1.8 g/cm3.

However, the process of demolishing the high right bank is going to come to an end fairly soon — as soon as a new profile of equilibrium has been form-ed in the submerged part of the inclined bank slope and a new beach strip develops. While this process is under way, deposition of washed-down bank material in this basin zone is bound to grow steadily less, and finally to lose its influence upon the nature and the rate of basin silting. —

In the remaining part of the zone occupied by the former Vistula channel, practically no deposition of a clayey, nor even a silty fraction is taking place, apart from filling local deeper depressions. The reason is, that compared with other areas submerged after river ponding, the former Vistula channel has a fairly well smoothed bottom and profits therefore from much better flow

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conditions. Hence this former river channel continues to be a zone of more rapid flow with velocities much higher then in the remaining zones, and up to 80% of all water passing through the reservoir is moving in this zone. Under flow conditions like these, only a slight accumulation of mainly medium grai-ned sands can be expected to take place here.

Dark, greenish-brown clayey silts with a considerable (5-10%) content of organic material and a specific gravity of 1.1 to 1.5 g/cm3 are deposited in great quantities, yet at a fairly varying rate (from 0 - 3 0 cm, and some 10 cm on the average) mostly in the zone of the former flood terrace where these silts fill, first of all, most of the previously depressed parts of the terraces.

Finally, it is worth mentioning that in the shallow water covering a strip some 200 m wide or more along the western bank of the basin, wave action contributes to levelling of the initially uneven sandy bottom. The thickness of the fine grained, sometimes clayey, depositis indisputably determined at paces where on submerged turf bottoms exact measurements were possible, proved to be from 6 to 25 cm; these deposits vary (from 1 to 10%) in the amount of organic material they contain. Also divergent is their specific gravity, ranging from 1.2 to 1.8 g/cm3. Still, on the whole, it seems that during today's early stage of basin evolution, the effects of erosion and accumulation are cancelling each other out.

To sum up, we see from our investigations and observations that the feat-ures of sedimentation and the intensity of deposition reveal wide differences in both the transverse sections and in the longitudinal profile of the reservoir. As was said before, processes of abrasion occur at a high rate on the high north-ern bank, of bottom erosion, and of redeposition of deposits, especially in the wide shallow-water zone extending along the southerm bank of the reservoir. And these facts explain why, in the size frequency of the mineral part of the deposits from all zones of the basin, the fine grained and silty fractions marked-ly predominate.

During the present-day initial stage of reservoir formation all the processes and phenomena reported above are taking place with particular intensity. This is caused by the differences in flow velocities in the particular zones and parts of the reservoir due to the complex relief of its recently submerged bottom zone and to the action of waves, so particularly effective where the water is shallow.

But, gradually, the result of all these processes leads to a step-by-step sta-bilization of a new bank line, to the formation of a new profile of the submer-ged scarp in the slopes of the reservoir bowl, and to a general levelling of the reservoir bottom. Only the channel zone of the previous Vistula flow is going to maintain its modified but still smooth profile. From what has been said so far about the complex character of the reservoir and the differences observed within it, and about the gradual changes anticipated due to processes of sedi-mentation and accumulation, it can readily be seen that at the present stage it would be difficult to define values of the probable annual growth of the bottom deposits with regard to the whole bottom surface of the reservoir and on this basis to estimate the duration of the expected useful life of the reser-voir. Our measurements indicate, that the deposits may grow in height along the order of 0.-5 to 1.5 cm per year.

Adopting preliminary assumptions similar to those applied for the Zegrze Reservoir one may presuppose in a first approximate estimate the useful life of the Włocławek Reservoir to be 400 to 600 years; should a neighbouring basin be constructed near Wyszogród, at least 50% would have to be added to the life of the Włocławek Reservoir.

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It is impossible to supply a more detailed forecast until the next series of measurements is made, after a period of at least some 10 to 15 years. By this time all processes transforming the banks and the bottom of the reservoir should be much mitigated. At present, only a few years since the Vistula has been ponded at Włocławek, all these changes are taking place rapidly and therefore they very much obscure the image of the true rate at which the reservoir is being filled with deposits.

RECAPITULATION

As has been demonstrated in the first chapter, the methods so far in use for appraising the rate of filling storage reservoirs with deposits and estima-ting their useful life cannot be expected to yield satisfactory results. The rea-son is, that on the one hand these methods are based on most unreliable source data and, on the other, that they fail to take into account phenomena and processes, continuous or periodical, which may often cause essential changes in local conditions of sedimentation and in the rate of blocking up the reser-voirs — changes either liable to speed up or to delay these processes.

Among agents delaying basin silting should be mentioned what is called "self-purging", "settling" of the deposits during periods when reservoirs are drained, or settling them due to wind-actuated waves. On the other hand, one factor accelerating silting is a vigorous growth of organic life in the basin and in the rivers feeding the reservoirs.

In the Zegrze and the Włocławek Reservoirs "self-purging" occurs during flood periods in the Narew-Bug valley and the Vistula valley. When the sluice-gates are fuily open, both these reservoirs turn into rapid-flow rivers (at 1 to 2 m/s), and this causes much of the deposits earlier laid down to be swept away. Admittedly a high-water flow also brings into the reservoir a greater amount of material; yet, apart from back-water zones, removal of bottom de-posits during flood periods definitely surpasses deposition of newly brought-in material.

Periodical drainage of reservoirs leads to an extension of their useful life because, when a reservoir has run dry for a sufficiently long time, say several months, all over the exposed surface a definite "settling" of the deposits takes place, in conséquence not only of the rapid decomposition of the organic sub-stances the deposits contain, but also due to dehydration and desiccation. The effect is, that the thickness of the deposit may be reduced 30 to 50% or more; most often this is an irreversible process, meaning that upon the reservoir being filled with water the deposits are not going to „swell" back to their orig-inal volume. This observation was confirmed by studies made in the periodi-cally drained Pilichowice, Leśna and Złotniki Reservoirs (T. Stokłosa, 1960; A. Jahn, 1968), as well as by the results of experiments made on deposits taken f rom the Włocławek and the Zegrze Reservoirs.

The effect of wind-actuated waves upon the reduction of silting processes can only be observed in fairly shallow reservoirs and in those parts of deeper basins where water movement caused by waves extends down to the top sur-face of the deposits. Water mixing, often also stirring of the uppermost semi-liquid layer of the deposits, increases oxydation dî the deposits and, in this way, leads to a more rapid and a more thorough decomposition of the organic ma-terial they contain. Moreover, this water movement, causing washing away of the upper deposits and converting them into a layer of suspended matter, will of ten cause part of the stirred-up deposits to be carried off beyond the reser-

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70 K. Więckowski

voirs. Finally let it be understood, that a strong wave action, continuously shifting from place to place the sands and gravels spread over the bottom, effectively counteracts the growth of aquatic vegetation, both of submerged plants and of the "hard-stem" reeds. Proof of this also is the lack of aqueous vegetation in the windward parts of the bank zone of many lakes — in spite of the fact that here extensive shallow water zones occur.

In the two reservoirs under discussion, extensive zones of shallow water fringe these kinds of "windward" southern lake banks. With these parts of the reservoirs gradually becoming more shallow, the favourable effect of wave action may be expected to continue and increase; afterwards it would seem that, after arriving at some critical value (say about 1 m depth), fur ther silting of the shallow lake zone may cease altogether.

On the other hand, biological life thriving in the reservoirs and the rivers feeding the reservoirs is apt to speed up the rate of reservoir silting. Even now, as mentioned before, products of lifeless flora and- fauna constitute some 10°/o of the deposits. Yet one must anticipate that in future, due to man's economic activities, the eutrophy of open waters, rapidly occurring almost everywhere is going to stimulate biological life in our two reservoirs also and, in this way, suitably to increase the amount of organic substances in the deposits. Most harmful here is the growth of both "hard-stem" and submerged vegetation, i.e. the formation of what is called "submerged meadows". This process is known to cause large quantities of plant remnants to be deposited on lake bottoms and to "smother" water motion, so that most of the material suspended in the wa-ter is going to drop to the bottom.

Hence, unless effective and inexpensive methods of counteracting plant growth are invented, our estimates of the useful life of shallow reservoirs sim-ilar to those at Zegrze and Włocławek, based solely upon their rate of silting in their initial stages of formation, may prove much too optimistic.

To sum up, our investigations reveal that the method of estimating the rate of reservoir silting based on direct measurements of the thicknesses of the deposits during the reservoir life yields auspicuous results. Its disadvantage is, that extraction of cores of deposits from a great number of points demands much time and effort; yet it is indispensable for obtaining reliable mean wal-ues for the rate at which a given reservoir or parst of it are silted up. A fur th-er drawback may at times be the difficulty of establishing the boundary between the original lake bottom and. the deposits — especially within pre-vious river channels, in the zone where back-currents occur.

It is essential to remember that for reservoirs situated in the lowland reliable results can only be obtained from investigations made some 20 to 30 yęars after the reservoirs were constructed. This period of time is required to let processes of bank abrasion, of the formation of new balanced bank profiles in the submerged parts of the reservoir slopes, and of smoothing initial bottom depressions subside suffciently so that they do not obscure the image of real accumulation of deposits and of reservoir silting — as is the case in the initial period of their existence.

REFERENCES

Basiński, T., Robakiewicz, W., 1964, Pomiar głębokości zbiornika rożnowskiego przy zastosowaniu echosondy (Depth measurements by the use of echo-sounding in the Rożnów Reservoir), Gospodarka Wodna, 3.

Brański, J., 1966, Pomiar transportu rumowiska unoszonego jako ważnego elementu przy projektowaniu budowli wodnych (Measurements of t ransfer of material in

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The silting processes 71

suspension — an important element in designing hydraulic structures), Gospodar-ka Wodna, 10.

Brański, J., 1968, Charakterystyka transportu rumowiska unoszonego w rzekach pol-skich (Characteristics of t ransfer of material in suspension in Polish rivers), Gospodarka Wodna, 11.

Cyberski, J., 1969, Sedymentacja rumowiska w zbiorniku rożnowskim (Debris sedi-mentation in the Rożnów Reservoir), Prace PIHM, 96.

Dębski, K., 1959, Próba oszacowania denudacji na obszarze Polski (Attempt to estimate denudation in Poland), Prace i Studia Komitetu Gospodarki Wodnej, vol. 2, 1, Warszawa.

Dojlido, J., et al., 1967, Charakterystyka limnologiczna wód Narwi i Bugu przed i po utworzeniu jeziora zegrzyńskiego (Limnological characteristic of the Narew and Bug waters before and after ponding the Zegrze Reservoir), Prace Inst. Gosp. Wodnej, vol. 4, 3.

Jahn, A., 1968, Geomorfologiczne wnioski z obserwacji dna jeziora zaporowego (Geomorphological conclusions drawn from observations of the bottom of a sto-rage reservoir), Czas. Geogr., vol. 39, 2, pp. 117-123.

Mikulski, Z., Chomiak, Z., 1963, Akumulacja rumowiska rzecznego w zbiorniku pili-chowickim (Accumulation of fluvial dr if t in the Pilichowice Reservoir), Gospo-darka Wodna, 12.

Onoszko, J., 1962, Zamulanie zbiornika rożnowskiego (The silting of the Rożnów Re-servoir), Rozprawy Hydrotechniczne, 12.

Onoszko, J., 1964, Zamulanie zbiornika rożnowskiego w 19-leciu jego eksploatacji (The silting of the Rożnów Reservoir af ter 19 years of its exploitation), Prace własne IBW PAN, Warszawa-Poznań (typescript).

Prognoza intensywności zamulania zbiorników wodnych (Forecast of intensity of silting up of water reservoirs), 1970, Instytut Gospodarki Wodnej, Materiały Konferencj i Naukowej „Badania naukowe i postęp techniczny w dziedzinie gos-podarki wodnej. Budownictwo wodne", vol. 2, Warszawa.

Reniger, A., 1959, Zagadnienie erozji gleb w Polsce (The problem of soil erosion in Poland), Prace i Studia Komitetu Gospodarki Wodnej, vol. 2, 1, Warszawa.

Stokłosa, T., 1960, Osuszenie zbiornika zaporowego w Pilichowicach (Dewatering the Pilichowice storage reservoir), Geografia w Szkole, 1.

Więckowski, K. 1968; Geneza, wiek i ewolucja jezior NE Polski (Origin, age and evolution of lakes in NE Poland), Folia Quaternaria, 29.

Więckowski, K , 1970, New type lightweight piston core sampler, Bull, de l'Academic Polonaise des Sciences, ser. geol. et geogr., 18, 1 (July).

Wiśniewski, B., 1963, Pomiar zamulania zbiornika wodnego w Otmuchowie (Measu-rements of silt accumulation in Otmuchów Reservoir), Prace Inst. Gosp. Wodnej, vol. 2, 1.

Wiśniewski, B., 1966, Badania odkładania się rumowiska w zbiornikach wodnych (Investigations of debris deposits in water reservoirs), Inst. Gosp. Wodnej. Ma-teriały Badawcze, vol. 2, 1.

Wiśniewski, B., 1969, Zamulanie zbiorników wodnych w Polsce oraz próba jego prog-nozy na podstawie intensywności denudacji (The silting up of water reservoirs in Poland and a tentat ive forecast based on intensity of denudation), Archiwum Hydrotechniki, 4.

Wiśniewski, B., Intensywność zamulania zbiorników wodnych w Polsce (Intensity of silting up of water reservoirs in Poland), unpublished.

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GEOGRAPHIA POLONICA 41, 1979

L A N D S C A P E F A C T O R S M O D I F I E D B Y A G R I C U L T U R A L A C T I V I T Y

SÁNDOR MAROSI, SÁNDOR P A P P

Geographical Research Institute, Hungarian Academy of Sciences, Budapest

1. The title of our paper suggests a very broad theme. It is well known that in the course of social development, mankind has extended its agricultural activity over large areas in order to meet the demand for more food and, by doing this, has significantly transformed the natural environment. At the same time, man has altered the progress of natural processes preceding human im-pact.

In our short paper we obviously cannot undertake even a roughly outlined survey of this group of problems, and neither do we see it as our task to discuss general theories. Instead we briefly analyse the changes that take place in a selected model area, the alteration of the natural processes as a result of agricultural production. Our aim is to determine the possible effects of fur th-er intervention. • By selecting the model area from among about 15 representative* agricultu-

ral areas examined with the help of L. Góczán and J. Szilárd, we have decided to discuss the following area because it is representative of extensive areas owing to its geographical location in Hungary and its morphological character-istics.

The model area represents high and low flood-plain surfaces lying along the Danube, south of the capital, on the Csepel island (Fig. 1). As a result of detailed investigations we were able to reconstruct the effect of flood control and river regulation in the area, water management being regarded as an anthropogenic activity. It was in the light of this latter precondition that the effects of agricultural activity on the natural processes were evaluated. How-ever, there was another reason for our choice of a flood-plain model area as the theme of our paper and this is the fact that such areas are common in Poland and thus an exchange of views and experiments may be possible.

2. Apart from some terrace islands originating at the end of the Upper Pleistocene (Il/a), which were flood-free in historical times and remained so even during the catastrophic flood of 1838 (Fig. 2) and therefore attracted set-tlements, the difference between the high flood plain and low flood plain of the Danube is generally only 5 meters (Fig. 1). Danube gravel is the homo-geneous alluvial material. On the terrace islands it is overlain by wind-blown fluviatile sand, on the flood-plains by fluviatile sand, and to a smaller extent by silt and clay. On the surface loess-silt is the characteristic sediment. This latter is a characteristic soil-forming rock along the Danube; it is a typical flood-plain sediment (Fig. 3).

3. Before the regulation of the Danube and preceding the time when flood-control measures were introduced in the 19th century, the Danube co-vered the island with a network of channels, the majority of which were under

6 Geographia Polonica 41 http://rcin.org.pl

F i g . 1. P l e i s t o c e n e a n d H o l o c e n e s u r f a c e s on t h e C s e p e l i s l and , i n t h e e n v i r o n s of o u r s e l e c t e d m o d e l a r e a

1 — the Il/IIa terrace of the Danube of late Pleistocene age covered with sand dunes; 2 — low and high flood-plain levels: the latter is characterized by a dense network of infilled abandoned channels (filled in by 1 or 2 m ' t h i c k alluvium). See Figure 4 which is on a larger scale. A-A' — profile shown on Figure 3; B — model afea shown on Figure 5; C — site of the

geomorphological map shown on Figure 4

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Landscape factors 75

Fig. 2. Areas inundated during the flood of 1838 (horizontal shading) on the Csepel island.

Taken f rom the book Pest-budal arvlz 1828-ban (The 1838 flood in Pest-Buda)

water only during floods (Fig. 4). This is especially typical of the southern part of the island, whose southward extension was due to point bar formation.

The natural mechanism of the river was thoroughly altered by the regu-lations. Prior to the regulation, the river could spread over vast areas during floods and the maximum flood-water level was lower than it is today: it sel-

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76

w

S. Marosi, S. Papp

E

m

Fig. 3. Profi le of the area f rom the Danube a rm at Budafok to the br ick-works at Gubacs constructed by S. Marosi

1 — Mediterranean layers; 2 — Sarmatian limestone; 3 — Pannonian sediments; 4 — Pleistocene debris-gravel cone; 5 — Upper Pleistocene gravel; 6 — Upper Pleistocene fluviatile sand; 7 — Early Holocene fluviatile sand; 8 — Early Holocene calcareous mud (loess-mud); 9 — Late

Holocene calcareous mud (loess-mud); 10 — blown sand; V — fault

dom inundated the upper flood-plains. As a result of this, soil formation could go on undisturbed until it became a stepp (chernozem) soil. On these upper flood-plains, since inundation seldom occurred, it scarcely resulted in the accu-mulation of sediments (shallow water); they only altered the dynamics of cher-nozem soil formation towards a semihydromorph condition. Steppe vegetation was characteristic of these areas. On the low flood-plains, 2-4 metres lower, abandoned channel sections and oxbows were common. They were seasonally inundated, and the area was either covered by open waters or had a moor-swamp vegetation.

Fundamental changes were brought about by the regulation of the river: it changed the mechanism of the stream, forced the river into embankments and, from Budapest down to the region of Dunaujváros, into two beds. Con-nected with the above were changes in the quantitative-qualitative features of the natural processes and also an alteration in the ecology of the whole region.

a) The Danube is restricted by dams into narrow belts and thus floods in the main channel culminate at higher water level than formally. (This refers to the main channel at Budafok, and does not affect the Ráckeve-arm of the Danube which is regulated by the Kvassay flood gate). Erosion is more active in the restricted channel, and more humid ecological conditions characterise this area. (On the banks more homogeneous successions developed: Salix, Po-pulus, Alnus-species and Cornus sanguínea, Crataegus etc. At the same time the possibility of the homogenization of the natural processes increased in the flood-free areas. Former yearly inundation of abandoned meanders ceased on the high flood-plain and their role was taken over (though on a smaller scale) by the inland waters which were linked with the now higher floods of the Danube. Thus the meanders were gradually drying out as both qualitative and quanti-tative factors played a role in the direction of their development, not to men-tion the most, important event — the reduced frequency of floods. This result-ed in the following: the former river-beds became oxbow lakes, and began to dry out gradually. They were infilled by mineralogic and organogenic sedi-ments and-the prevailing ecological conditions became somewhat more similar to those of the upper flood-plains. On the upper flood-plains the danger of inun-dation became remote and ceased to exist, and the natural steppe-forming processes (in soil geography called chernozem dynamics) became apparent.

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Landscape factors 77

Flood-control regulations meant that additional areas were now available for agricultural purposes, and the range of possibilités for land use increased. The upper flood-plains could be used for a whole rangé of plant cultivation, for f rui t and vine cultivation. This was made possible by the soil-forming rock as well as by the soils that had formed on these. However, it must still be ta-ken into account in the course of agricultural utilization and when selecting suitable plants that the soils have a high carbonate content: it is the C-horizon which shows an especially high CaC03 content.

b) Agricultural use was gradually extended — as a result of protection against inundations and because of the process of filling up — to the lower flood-plain levels represented mainly by abandoned river channels (Fig. 4). First meadow cultivation, then the cultivation of agricultural plants that prefer moist soils was undertaken and, after the danger of inland waters had passed in spring, late sowing would follow. A gradually more and more intensive use of the land by man resulted (as a consequence of increased water consumption) in the drying out and filling up of the abandoned river channels. Regular ploughing causing the continual disturbance of the soil surface contributed considerably to the increase of soil erosion in the abandoned river channels, especially at their steep margins. The material degraded from both the higher levels and from margins of the abandoned channels accumulated in the for-mer beds and the surface became more or less levelled. The whole area is now under cultivation. It has a rolling surface characterized by a shallow depression of 0.5-2.0 metres (Fig 4). Only in the southern part of the island — which was the most typical area of abandoned channel sections and of former meanders before the regulation of the river — there are still some oxbows filled with the inland waters at spring. Abandoned channels with narrow steep slopes of 2-3 metres are used as pasture or under meadow cultivation.

As on all surfaces with some potential relief energy under agricultural tillage, soil erosion increased in the area. Apart from the danger of soil ero-sion, there is, however, a fu ture advantage, namely, the constant levelling off and filling up of the surface of the abandoned channels. This can only be attain-

0 BOO 1000 m 1 i i

Fig. 4. Pa r t of the geomorphological map of the model area showing the infilled abandoned river channel network, and separated into low and high flood-plains

(constructed by L. Goczan, S. Marosi, S. Papp and. J. Szilard) 1 — upper flood-water level no. 1 (on average 98 m a.s.l.), 2 — upper flood-water level no. 2 (on average 97 m a.s.l.), 3 — lower flood-water level no. 1 (on average 96 m a.s.l.), 4 — lower flood-water level no. 2 (on average 95 m a.s.l.), 5 — infilled abandoned river channel, 6 — shallow

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78 S. Marosi, S. Papp

ed by an accelerated soil-forming process induced partly by agricultural activity. This would result in the formation of anthropogenic soils in place of the present narrow, barren strips which, however, cover extensive areas.

4. Our brief discussion does not permit us to go into a fur ther detailed analysis, and we must conclude with the following summary. In the model area and on the flood-plain, as a whole, embanking of the river considerably extended the possibilities of agricultural activity in the areas no longer endan-gered by floods. It sometimes led, however, to the formation of the kind of soil water table that promotes alkalization. We do not discuss this later problem in our present paper. As agricultural activity increased and the significance of linear erosion lessened under the new geomorphological conditions (decreasing relief energy) the role of areal erosion increased. This was influenced in the first place by the amount, frequency and intensity of precipitation. The effect of this could, however, be more marked on the disturbed cultivated sur-faces and manifests itself in the form of increased soil erosion. This resulted in morphological changes. It is a seasonal phenomenon, but it must be reckoned within land use.

A consequence of agricultural activity on flood-plain surfaces is the so-cal-led soil-climatic drying (L. Goczan, 1972b) due to agrotechnical methods and the different moisture demand of cultivated plants. This asserts itself in terms of soil dynamics by a gradual drying out of the soils: in our model area, and in the flood-plain area as a whole the hydromorphic and semihydromorphic processes become less important.

This process contributed to the formation of zonal soil types in the flood-plains along the Danube. Chernozems prevail and the meadow soils turn into chernozem-meadow and meadow-chernozem soils, and finally to chernozem.

*

It will be seen from the above that as a consequence of agricultural activity following river regulation and flood control, the former more diversified and varied soil genetic groups underwent important changes and the entire land-scape ecology was fundamentally altered and became more homogeneous. At the same time, the natural productivity of the soils also were homogenized. Thus the genetic soil types could be treated by agricultural land use and for agrotechnical purposes as typical of a more uniform large homogeneous area (homogeneous, agroecotypes; Fig. 5).

Our method of investigation was as follows: 1. We determined the average productivity value of the genetic soil types

and attributed point values to each (basic value figure). These values represent together with the modifying factors all environmental factors — including those occurring as a consequence of human activity. The total value of these latter are indirectly reflected in the genetic soil type.

2. All the environmental factors were also attributed point values inclu-ding soil properties, the presence or absence of which influenced locally the average productivity value of the genetic soil type in question (modifying factors).

3. After combining the basic value figures and the values of local modifying factors, the total productivity value of a genetic soil type was determined.

4. The obtained values were classified and represented on maps (Fig. 5). The following general conclusion may be drawn: man's agricultural activity produces such far-reaching changes in the landscape (not only in flood-plain areas!) that it must be regarded as the most important landscape, and soil

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Landscape factors 79

forming factor. In agricultural areas some of the natural processes may cease to be active or their role may be reduced. The modifying effect of other natu-ral factors may, however, assume particular importance because of the new conditions brought about by outside factors. These new processes were for-merly either inactive or latent without the motivating force of cultivation and agricultural activity.

Fig. 5. Agroecological units of a typical flood-plain area (Lôrév-Makâd on the Csepel island) compiled by K. Molnâr and S. Papp

Selected value classes for agroecological potentials (combined categories): 1 — outstanding potentials (10-12 points on map), 2 — good (8-9 points), 3 — moderate (6-7 points), 4 — poor

(3-5 points), 5 — agroecological types with very poor potentials (0-2 points alloted).

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80 S. Marosi, S. Papp

REFERENCES

Göczän, L., Marosi, S., Szilärd, J., 1972a, Duna-völgyi ärteri t ipusterület (Lörev-Ma-käd) agrogeolögiai viszonyai (Agrogeological conditions in the model area of Lörev-Makäd on the flood-plain of the Danube), manuscript, Budapest, MTA Földrajztudomänyi Kutatö Intezet.

Göczän, L., Marosi, S., Szilärd, J., 1972b, A mezögazdasäg termeszeti eröforräsainak agroökolögiai elemzese kelet-kisalföldi t ipusterület peldäjän (Agroecological evaluation of natural potential for agricultural use in the model area in the eastern par t of the Litt le Hungarian Plain), Földr, Ert., 21, pp. 14-41.

Göczän, L., Marosi, S., Szilärd, J., 1972c, Az agrogeolögia mai igenyeknek, követel-menyeknek megfelelö kutatäsi tärgya, mödszerei (The subject and methods of agrogeological research in the light of present-day demands and expectations), manuscript, Budapest, MTA Földrajztudomänyi Kutatö Intezet.

Göczän, L., Marosi, S., Szilärd, J., 1974, ökologische Kart ierung von agrogenen Ge-bieten, Földr. Ert., 23, pp. 207-218.

Haase, G., 1964, Landschaftsökologische Detailuntersuchung und naturräumliche Gliederung, Petermanns Geogr. Mitteilungen.

Isachenko, A. G., 1962, Ucheniye o landshafte i fiziko-geograficheskoye rayonirova-niye, Izd. Leningradskogo Univ.

Magyaroszög vizboritotta es ärvizjärta területei az ärvizmentesitö es lecsapolö munkälatok megkezdese elött, 1938, Inundated areas affected by floods before the regulation of the r ivers in Hungary, Terk6p (a map) Budapest, Földmüv. Min. Vizrajzi Lntezete.

Marosi, S., 1955, A Csepel-sziget geomorfolögiai problemäi (Geomorphological prob-lems of the Csepel-Island), Földr. Ert., 4, pp. 279-300.

Marosi, S., Szilärd, J., 1964, Landscape evaluation as an applied discipline of geog-raphy, Studies in Geography in Hungary, 2, pp. 20-35.

Marosi, S., Papp, S., Szilärd, J., 1973. Mikroökolögiai adatok Düna menti artjeri fel-szlntipusok elkülönitesehez (Classification of land surface-types into ecological units on the basis of microecological data on the floodplain along the Danube), Földr. Ert., 22, pp. 33-53.

Marosi, S., Papp, S., Szilärd J., 1975. Dunäntuli reprezentativ tipusterületek agroge-ologiai vizsgälatänak összegezö ertekelese (Evaluation of the model areas selec-ted in Transdanubia for the examination of agrogeological type-areas), manus-cript, Budapest, MTA Földrajztudomänyi Kutatö Int.

Mukhina, L. I. (ed.), 1969, Metodi landshaftnikh issledovanity, Moskva, Izd. Nauka. Neff, E., 1967, Die theoretischen Grundlagen der Landschaftslehre, Gotha, VEB Her-

mann Haack. Pecsi, M., 1969, A magyarorszägi Duna-völgy kialakuläsa es felszinalaktana. (For-

mation of the Danube valley in Hungary and its morphological characteristics), Budapest, Akademiai Kiadö, Földr. Monogr., III.

Pecsi, M., 1971, A domborzati egyensüly megvältozäsa az ember müszaki-gazdasägi tevekenysege következteben (Changes in the state of equilibrium of the topo-graphy as a result of mans technical and economic activities), MTA, Biol. Oszt. Közl., 14, pp. 29-37.

Troll, C., 1966, ökologische Landschaftsjorschung und vergleichende Hochgebirgs-forschung, Wiesbaden, Franz Steiner Verlag. \

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Fig. 2. Stratigraphic profile of the Also-Oreghegy hill at Dunafoldvar on the basis of borehole data A. Eolian sediments: 1 — sandy loess; 2 — loess; B. Colluvial, deluvial sediments; 3 — sandy loess, stratified fill of a buried derasional valley; 4 — pink-coloured fine sandy-silt; 5 — stratified loessy-sand; 6 — stratified loess; C. Fluvial-p-roluvial sediments: 7 — sand; 8 — silty fine sand; 9 — silty sand; 10 — Fe, Mg coloured patches in clay; 11 — brownish-yellow CaC03 concretions in silty-clay; 12 — sandy gravel; D. Recent and fossil soils: 13 — humus carbonate soil; 14 — steppe-type soil; 15 — chernozem brown forest soil; 16 — brown forest soil; 17 — semipedolite; 18 — hydromorphic soil; 19 — alluvial marshy soil; 20 — CaCOs accumulation; E. Pannonian: 21 — grey-yellow clay; 22 — grey-yellow silty sand; 23 — snd; F. Anthro-

pogenic constructive forms: 24 — anthropogenic fills

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GEOGRAPHIA POLONICA 41, 1979

C H A N G E S I N T H E G E O G R A P H I C A L E N V I R O N M E N T A S A R E S U L T

O F O P E N M I N I N G

LEON KOZACKI

Institute of Geography, Adam Mickiewicz University, Poznari

Land features formed as a result of open mining play an important role among anthropogenetic forms which occur in the Polish landscape. They con-sist of all kinds of deep pits of various sizes, slope pits, slope recesses, and a number of other forms. According to the resources which are being exploited, the type of land where the mining takes place (regional and morphological), and the method of exploitation, the resulting anthropogenetic forms will all be very different. The degree of interference with and influence on the sur-rounding environment will also differ. With reference to the method of exploi-tation the following question arises: are dumping of the overburden and drai-ning of the bed necessary to obtain a given mineral?

Generally, the above forms may be divided into forms which only locally influence the area and forms of some wider influence on the surroundings. Changes caused by open mining of brown coal are one of many examples of the latter group. The detailed mechanism and range of changes are shown in Fig. 1.

However, according to the author it is not enough to establish facts eviden-cing man's interference with the geographical environment. The geographer's task is to develop methods of forecasting changes in the geographical environ-ment, and then to determine the forecast itself. That is in agreement with the basic principles for the development of physical geography, and with the tasks set before that discipline by the economic needs of a country (Z. Chojnicki, B. Gruchman, S. Kozarski, 1967; S. Kozarski, 1975).

The author would like to make some remarks about methods forecasting changes in relief on the basis of investigations carried out in the Konin Coal Basin and in some coal basins in the GDR. The starting point for analysis of fu ture changes, and thus analysis of relief forecasting, should be a detailed knowledge of the original situation. However, in the case of mining on a large scale, this requirement has not always been met. Knowledge of the present situation must include the geomorphological characteristics of the area (map with description) of the future basin against a wider background in order to indicate or exclude some relationships and interdependent factors. The area of the coal basin itself should have a detailed map of its slopes. But because of strong interrelations between factors of the geographical environment, fore-casting of changes in relief will be accurate only when one takes into consi-deration the relationship of relief to geological and hydrological conditions, or to other elements (L. Kozacki, 1965, 1972). It will also be very important to know the technological background to the mining activities and in particular,

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84 L. Kozacki

— Possibility of cyclic recordings. Repeating of recordings allows for a close observation of changes, which is the basis for discovering tenden-cies, and hence it provides some basis for forecasting.

Because of these requirements it is impossible to use the method of the instrumental topographic photograph, which is very detailed but takes too much time and does not allow everything to be recorded at once. Since a pic-ture of the open mine changes very quickly, above-ground photogrammetry avoids some negative features of the previous method. However, it should be taken into account that so-called "dead fields" may occur, resulting in a incom-plete picture.

The method that secures cyclicity and allows forms and phenomena to be recorded at once in the whole of the area under investigation is the use of pho-togrammetric aerial photographs (Liedtke, 1963; L. Kozacki, 1969). At the same time, the detail obtained allows one to detect the development or alterations occurring in microrelief which is so characteristic of anthropogenetic forms (M. Z. Pulinowa, 1972; J . Repelewska-P^kalowa, 1973). When it has been deci-ded that aerial photography will be the main method, still the other two met-hods cannot be excluded. They may be used as additional methods in f ragmen-tary investigations or in investigations of some narrower thematic range. The use of aerial photography is fur ther supported by the fact that it records all the processes and phenomena occurring on the surface and in sub-surface zo-nes, this enables one to use the material obtained for analysis and to develop forecasting of changes within other areas of the geographical environment. This refers to surface waters, to the uppermost level of underground waters, to the surface geological structure, which altogether contribute to the knowl-edge of hydrological and geological-engineering conditions (R. Beaver, J. Wood. 1974). This also refers to soils and vegetation.

From the aforementioned wide application of aerial photography arises the question: in what periods should photogrammetric flights take place, so that the material could be used for various analyses. As can be seen from the accom-panying plan of stages for the forecasting of changes in relief, photogrammetric flights for that type of forecasting should be made in the following periods (phases):

— after recognition of deposit, before exploitation (I), — after heaping of the outer dump (II), — after the end of draining and the end of exploitation (III), :— alter all reclamation is finished (IV). It seems that moments captured on aerial photographs will be crucial not

only for analysis of relief but also for analysis of other elements of the geo-graphical environment. Only during the preliminary photographing it should be remembered that photographs should be taken not only before the mining itself (opening dig) but also before preparatory works, such as draining of de-posits, shifting of flows, surface draining, buildings of roads, forest clearing, etc. With regard to the last photogrammetric flight, it may be necessary to plan the date with more care, or even to plan an additional flight so that the ana-lysis, and therefore the forecasting, would be complete.

In the Konin Coal Basin the brown coal is exploited from various pits started at different times, so that they are at various stages of development. Therefore, while taking aerial photographs of one which is at some definite stage of development it is possible to find a picture of another pit which is at another stage or at an intermediate stage. The documentary material is then greatly enriched.

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Changes in the geographical environment 85

On the basis of aerial photographs of the area of the open pits "Niesłusz" and "Gosławice" taken at the third stage of exploitation (that is after the end of draining and exploitation) a map of the changed relief with some elements of a morpho-dynamic map has been made (Fig. 3). Although in the normal cycle of a study the appended map is a part of the whole which enables us to see changes in the relief and its dynamics, a proper sign showing the dynamics also gives a good idea of the whole. The first application of that principle is a differentiation of artificial elements from natural ones by means of colour. All features of anthropogenetic relief, which in that case are connected with a direct mining activity, are marked in blue. These are surfaces of outer dumps, surfaces of inner dumps, slopes formed due to dissection of the surface during removal of overburden, traces of removal of brown coal deposits or overbur-den, surface of unlevelled ground dumping, longitudinal dumps and slopes of rolling-indented slopes. Contour lines illustrating the relief of areas not chan-ged by mining and all forms and signs which were formed and resulted from changes in the relief after the anthropogenetic activity has been finished, should be marked in brown. This is in agreement with the accepted rule for the indication of relief on topographical maps. In most cases brown signatures occur in combination with blue ones, which, on the one hand, underlines the character of a given feature or phenomenon, and on the other hand, according to the author, the morpho-dynamics of the relief are obtained.

The graphic picture of signatures in some degree has been based on Keys to a geomorphological map, whereas new signatures have been elaborated by the transformating of the picture presented on aerial photographs.

The time period during which the problem undertaken was studied did not allow for a complete observation of the phenomenon. This meant that it was possible to give a diagrammatic account of phase III only. The later picture of the relief after mining, and thus the general dynamics of the relief, and detection or determination of the basic zones, were possible only on the basis of studies comparative to post-mining areas in the German Democratic Re-public. Traditions of open mining of brown coal in the GDR are very old, and that is why features connected with that kind of human activity are quite nu-merous. Mines and post-mining areas in Lower Lusatia are the best area of reference for purposes of comparison (J. Pilawska, 1965, 1967). As follows from the initial part of the article, outer and inner dumps and final basins occur on the site of the open mine. The problem of the outer dump consists in the in-stability of its slope zone, and forecasting should take into account an increase in the length of the foot of the dump. There is no doubt that it will be influen-ced by the surface and height of the dump, the manner of overburden heaping, the manner of levelling of the upper surface, and by the kind of material dumped. It should be stressed that plants introduced there will play an impor-tant role in keeping the scarp stable. It will be strongly influenced by man's activity and a proper choice of plants. From the experiments carried out by the author it follows that in spite of proper reclamatory operations and proper choice of plants, the range of the outer dump foot has finally increased by 100%. Whereas processes of erosion, for obvious reasons, will largely affect the top zone of the dump. With suitable inclination, draining and economy that influence may be minimal. However, because this form is very specific the re-gime must be controlled by man.

Within the inner dump the problem of uneven subsidence of dumping and later of levelling material may occur, which results in the secondary rolling of the area. There may also occur small suffusional basins which lead to local wetness of the surface. In order to foresee tendencies, and in some degree also

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86 L. Kozacki

the extent of changes, the material collected in the second and third phases of forecasting will be used. It would also be advisable to record the movement of the ground from the point of view of lithological separation both in the hori-zontal and in the vertical sector. Particular attention should be paid to that side of the inner dump which will close the final basin. The process of change of relief within slopes of the outer dump is most intensive in the initial phase after heaping. But with the passage of time one may observe stabilization of the ground mass and a decrease in the intensity of the process and even its cessation. However, within scarps of the final post-exploitational basins, after their formation (dissection of the surface or heaping of the inner dump) there occurs quite a long process of mass movements (starting from the second phase) with signs of a gradual stabilization. The stabilization is stopped in phase IV when draining of the former area and the deposit also ceases. Raising of the underground water level and repeated watering of sediments within the "mainland" * and watering of the inner dump result in a renewed intensity of ground movement. Furthermore, the post-exploitational basin is filled with water and at the same time there occur processes of surface and underwater feeding, oscillations of the water level and processes of rolling. Altogether t iey strongly influence the slope area and unstable ground masses of the inner dump. On the basis of the evidence gathered in the Lower Lusatia Basin it may be said that it is a very intensive process and often catastrophic in its effects. It makes cultivation of post-mining areas very difficult. That is vhy the author marked places worthy of note with points or modal zones. In :his case the usefulness of forecasting is quite evident. Gathering of the basic in-formation about the original relief, geological structure, hydrological condi-tions, and particularly about the mechanism and dynamics of the underground waters of the first and deeper levels during the main stage of forecasting and completion of observations during fur ther stages make a basis for the optin.um forecasting of the relief development in the area discussed. However, from the point of view of economy the point is to reduce changes in relief which are so damaging and catastrophic. The stage of basic forecasting should deternine the character of fu ture utlization of adjacent areas together with some early change of vegetation, which may be of a decisive character there. It shculd also determine the necessity and range of hydrotechnical operations. Thus we see that forecasting should serve reclamative operations. There is no dcubt that reclamation must be based upon forecasting of changes in relief anc in other elements of the geographical environment, so that post-mining areas can be utilized in the best possible manner.

It may also be suggested that some elements of forecasting should be inclu-ded in the general plan of mining operations, and particularly in the plar of distribution of particular physical features since their topographic and envi-ronmental situation is not without significance for the future formation of the relief. This especially concerns the outer dump and post-mining final basin At the present time, the programmes which have been developed for reclamation are only partially based on forecasting studies, which makes them difficult or sometimes even impossible to realize. Only a total integration of the restorative programme in post-mining areas, on the basis of forecasting studies, with the whole spatial design can lead to a real restoration of areas devastated during mining works.

* This term is used by the author to refer to the area which has not been mecha-nically changed during mining works.

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Changes in the geographical environment 87

REFERENCES

Beaver, R., Wood, J., 1974, Aerial infrared locates solid ground over mine, Photo-gramm. Engin., 40, 2.

Chojnicki, Z., Gruchmann, B., Kozarski, S., 1967, Problemy rozwoju nauk geograficz-nych w świetle potrzeb gospodarki narodowej (Sum.: Issues of geography con-nected with the needs of the national economy), Przegl. Geogr., 39, 2.

Kozacki, L., 1965, Zmiany stosunków wód powierzchniowych i gruntowych między Kazimierzem Biskupim a Głodowem (Changes in the relationship of surface and ground waters between Kazimierz Biskupi and Głodów), Spraw. Pozn. TPN, 2.

Kozacki, L., 1969, Zastosowanie zdjęć lotniczych dla określenia zmian niektórych ele-mentów środowiska geograficznego na przykładzie Zagłębia Konińskiego (Use of aerial photography in the determination of changes of components in the geographical environment in the brown coal field near Konin), Fotoint. w Geogr., 7.

Kozacki, L., 1969, Analiza i ocena środowiska geograficznego powiatu konińskiego dla potrzeb prognozowania jego zmian (Analysis and evaluation of the geo-graphical environment in the Konin district and forecast of changes), Pozn. TPN, Prace Komis. Geogr. Geol., 6, 1.

Kozarski, S., 1973, Osiągnięcia i ogólne założenia perspektywicznego rozwoju geo-grafii fizycznej w Polsce (Sum.: Past achievements of physical geography in Poland and general perspectives of its development), Przegl. Geogr., 45, 3.

Liedtke, M., 1963, Bergbauland zwischen Saarbrücken und Neukirchen, Die Erde, 94, 2.

Pilawska, J., 1965, Rekultywacja terenu w zagłębiach węgla brunatnego Niemieckiej Republiki Demokratycznej (Sum.: R e c u r v a t i o n of the area in the brown coal basins in the GDR), Czas., Geogr., 36, 1.

Pilawska, J., 1967, Przeobrażenia środowiska geograficznego i rekul tywacja w pol-skich zagłębiach węgla brunatnego (Sum.: Transformat ion of the geographical environment and recultivation in the Polish brown coal fields), Czas. Geogr., 38, 2.

Pulinowa, M. Z., 1972, Procesy osuwiskowe w środowisku sztucznym i na tura lnym (Sum.: Sliding processes in artificial and natural environments), Dokum. Geogr. 4.

Repelewska-Pękalowa, J., 1973, Współczesne procesy mqrfogenetyczne na zwałach kopalnianych (na przykładzie odkrywkowej kopalni siarki w Piasecznie) (Sum.: Contemporary morphogenetic processes on quar ry dumps using the sulphur quar ry in Piaseczno as an example), Ann. UMCS, B, 28, 6.

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